Please select the column and the data types for the new NumberOfDays column.

Answer options:

A.Rollup
B.Duration
C.Whole number
D.Decimal number
E.Calculated
F.Auto-number

Correct Answers: B and E 
Microsoft Dataverse provides special column types for calculations and data aggregation. These types are Calculated and Rollup. 
The Calculated column allows users to define a formula based on the column value. This type includes columns from the same table and related parent table in a many-to-one relationship. Calculated columns are read-only. Users benefit from a list of built-in functions for the calculated values. This column type operates on the different data types like text, numeric, and date-time. The calculations run synchronously when a record is saved. 
The new NumberOfDays column stores the full days` value as Duration data type (Number 1). The column should be a Calculated type because you need to calculate the column`s value (Number 2).

If you rent a car today at 3 pm and return the day after tomorrow at 4 pm, you would rent it for 49 hours or two days and one hour. You need to store only two full days in a new field. In the Action section for the calculated column, you calculate the days` difference (Number 1). 

All other options are incorrect. 
For more information about The Dataverse Calculated and Duration columns, please visit the below URLs: 

https://docs.microsoft.com/en-us/learn/modules/create-define-calculation-rollup-fields/3-calculation
https://docs.microsoft.com/en-us/learn/modules/create-define-calculation-rollup-fields/3-calculation
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/customize/types-of-fields
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/types-of-fields