A.

Only one theme can be active at a time, and a theme applies to the entire org.

D.

Chatter external users see the built-in Lightning theme only.

Explanation: Themes are a way to customize the look and feel of Salesforce by changing the colors, images, and logos that appear on Lightning Experience pages. However, there are some limitations and considerations when using themes, such as: only one theme can be active at a time, and a theme applies to the entire org; themes apply only to Lightning Experience and do not affect Salesforce Classic or the Salesforce mobile app; up to 300 custom themes can be created, modified, or cloned from the built-in themes; Chatterexternal users see the built-in Lightning theme only and cannot see custom themes.

A.

Dependent Picklist

D.

Custom Picklist

A dependent picklist and a custom picklist are the two features that can be
used to fulfill the requirement. A global picklist and a multi-select picklist are not features that can be used to fulfill the requirement.
Here is a more detailed explanation of why A and B are the correct answers:
A. Dependent Picklist
A dependent picklist is a picklist whose values are dependent on the value selected in another picklist. This is useful for ensuring that only valid values are selected for a field. In this case, the administrator can create a dependent picklist for the category field on accounts and cases, with the values for the picklist being dependent on the record type selected. This will ensure that only the relevant picklist values are available for selection based on the record type selected.
For example, the administrator could create a dependent picklist for the category field on accounts and cases with the following values:
Record Type: New Account
Picklist Values: Residential, Commercial
Record Type: Existing Account
Picklist Values:Renewal, Upsell, Cross-sell
This would ensure that only the relevant picklist values are available for selection when creating a new account or an existing account.

B. Custom Picklist
A custom picklist is a picklist that is created by the administrator. This is useful for creating picklists with values that are specific to the organization's needs. In this case, the administrator can create a custom picklist for the category field on accounts and cases, with the values for the picklist being specific to the organization's needs. This will ensure that the picklist values are relevant to the organization and its customers. For example, the administrator could create a custom picklist for the category field on accounts and cases with the following values:

Picklist Values: Residential, Commercial, Land, Multi-Family This would ensure that the picklist values are relevant to the organization and its customers.

D.

Use Campaign Hierarchy where the monthly events roll up to a parent Campaign

Campaign hierarchy is a feature that allows administrators to organize
campaigns into a parent-child relationship, where the parent campaign represents a larger initiative and the child campaigns represent smaller or more specific activities within that initiative. Using campaign hierarchy can help Ursa Major Solar report on campaign ROI by month and series by creating a parent campaign for the series of networking events and creating individual child campaigns for each monthly event. The parent campaign can show the aggregated metrics and ROI for the entire series, while the child campaigns can show the metrics and ROI for each month. Adding different record types for the monthly event types, creating individual campaigns that all have the same name, or configuring campaign member statuses to record which event members attended are not solutions for reporting on campaign ROI by month and series; they either do not group campaigns into a hierarchy or do not track campaign metrics or ROI.
References:https://help.salesforce.com/s/articleView?id=sf.campaigns_hierarchy.htm&
type=5

B.

Configure an auto responserule to email thelead.

Auto response rules are a way to automatically send email responses to
leads or cases based on certain criteria such as lead source, industry, etc. They can be used to send personalized emails whenever a lead fills out a web-to-lead form on a website and send different messages based on the lead industry field value. Using validation rule to trigger workflow to email the lead is not possible because validation rules cannot trigger workflows or send emails; they only prevent records from being saved if theydo not meet certain criteria. Adding a public group and process builder to email the lead is unnecessary because auto response rules can handle this requirement without additional configuration
or customization. Creating an assignment rule to email the lead is also unnecessary because assignment rules are used to assign leads or cases to users or queues based on certain criteria, not send emails; although they can have email alerts as part of their actions, they are not as flexible as auto response rules for personalizing email messages.
References:https://help.salesforce.com/s/articleView?id=sf.customize_leadsauto
response.htm&type=5

B.

Validation Rule

Validation rules allow you to prevent users from changing an opportunity
close date to a date in the past.
References: https://help.salesforce.com/s/articleView?id=sf.validation_rules.htm&type=5

A.

Find them in the global search result.

C.

Utilize a list view where lead status equals Qualified.

Two ways that marketing users can now access converted leads for editing
are:
Find them in the global search result, by entering the lead name or other keywords in the global search box and selecting Leads from the drop-down menu. Converted leads will appear in the search result with a check mark icon next to them.
Utilize a list view where lead status equals Qualified, by creating or modifying a list view on the Leads tab and adding a filter for Lead Status equals Qualified.
Converted leads will have Qualified as their lead status and will be visible in the list view. Searching the Recent Records component on the homepage or using Data Import Wizard will not allow users to access converted leads for editing.
References: https://help.salesforce.com/s/articleView?id=sf.leads_view_converted.htm&type=5

D.

Existing auto number field to Text is prevented.

One thing that an administrator should be aware of before changing an autonumber field to text field is that this change is prevented by Salesforce; it cannot be done because it would cause data loss and inconsistency. Auto-number fields are fields that automatically assign unique numeric values to each record; they cannot be changed to text fields because text fields do not have this functionality and may allow duplicate or invalid values. Existing field values remaining unchanged, being converted, or being deleted are not things that would happen before changing an auto-number field to text field because this change cannot happen at all.
References:https://help.salesforce.com/s/articleView?id=sf.fields_about_auto_number.htm&type=5

A.

process builder

C.

Field Update

Process builder can be used to create a record-triggered flow that executes
when an opportunity is closed as won and creates a follow-up task for the owner. Field update can be used to update a date field on the opportunity that can be referenced by a time-dependent workflow rule to create another task after 60 days.
References:
https://help.salesforce.com/s/articleView?id=sf.process_which_tool.htm&type=5https://help.
salesforce.com/s/articleView?id=sf.workflow_time_action_considerations.htm&type=5