Flow Designer variables can store record data and complex data using the following data types:
Integer: A whole number that can be used in mathematical operations.
Array: A collection of items that can be accessed by their index or iterated over using a For each action.
String: Any kind of text, such as email addresses or the text contents of a file.
Reference:
Define and Use Data Types in a Flow (Flow Designer)
Variable data types - Power Automate | Microsoft Learn
Product Documentation | ServiceNow

The data type of a field determines the format, validation, and display of the field value on a form. When selecting a data type for a field, you should consider the purpose and function of the field. The statements A, C, and D are correct for selecting a data type for a field. For example:
Use the Choice data type to limit options in a field: The Choice data type allows you to create a field that has a predefined set of options for the user to select from. The options can be displayed as a drop-down list, radio buttons, or checkboxes. For example, you can use the Choice data type for a field that indicates the priority of a task.
Use the Phone Number data type to automate phone number data validation: The Phone Number data type allows you to create a field that accepts and validates phone numbers. The field will automatically format the phone number according to the user's locale and country code. For example, you can use the Phone Number data type for a field that stores the contact number of a user.
Use the string data type for a free-form text field: The string data type allows you to create a field that accepts any text input from the user. The field can have a maximum length of 255 characters. For example, you can use the string data type for a field that captures the short description of an incident.
The statement B is not correct for selecting a data type for a field. There is no Data data type in ServiceNow. To enter the date and time of day, you should use the Date/Time data type. The Date/Time data type allows you to create a field that accepts and displays a date and time value. The field will use a calendar widget and a time picker to help the user enter the value. For example, you can use the Date/Time data type for a field that records the due date of a task.
Reference:
[Field types]
[Date/Time field type]

See list of triggers on right hand side of this webpage: https://docs.servicenow.com/en-US/bundle/tokyo-application-development/page/administer/flow-designer/reference/flow-triggers.html The trigger types in Flow Designer are Application, Record, Schedule, and Topic. Outbound Email is not a trigger type, but an action type that can be used in a flow to send an email message1. Reference: Flow Designer Trigger Types

Extending an existing table such as the Task table when creating a new application has several benefits, such as:
You can repurpose existing fields by simply changing the label. For example, you can change the Short description field to Summary or Title for your new table.
You can use existing fields with no modifications. For example, you can use the Assigned to, Priority, and State fields for your new table without changing anything.
Existing logic from the parent table will be automatically applied to the new table. For example, you can inherit the Business Rules, Client Scripts, and UI Policies from the Task table for your new table.
The only option that is not true is d) All of the parent table records are copied to the new table. Extending a table does not copy any records from the parent table to the new table. It only creates a new table that inherits the fields and logic from the parent table.
Reference:
[Extend a table]
[Task table]