You want to change an inline function to a multi-statement function. Your major consideration is that modifying these user-defined Functions should not change the permissions of functions or affect any dependent functions. You decide to use ALTER Function, but you are not getting the desired results. What will be the best possible cause?

Answer options:

A.ALTER FUNCTION cannot be used to perform an inline function to a multistatement function modification.
B.ALTER FUNCTION can be used to perform only the Transact-SQL function to a CLR function.
C.ALTER FUNCTION cannot be used for modifying User-defined Functions.
D.ALTER FUNCTION always requires EXECUTE permission.

Correct Answer: A 
There are two ways to modify a user-defined function. One is using SQL Server Management Studio, and the second one is Transact-SQL.In this case, using ALTER function, which comes under transact SQL, the functions permissions, dependent functions, stored procedures, or triggers are not affected. 
But while using Alter function, the following should be considered or reverse. 
-> It cannot be used to change a scalar-valued function to a table-valued function or reverse. 
->It cannot be used to change an inline function to a multistatement function or reverse. 
-> It cannot be used to change a Transact-SQL function to a CLR function or reverse.
Option A is correct: It is one of the limitations in using Transact SQL for User Defined Function modification.
Option B is incorrect: Alter Function can be used with a wide variety of functions, not only CLR.
Option C is incorrect: ALTER FUNCTION is generally used for modifying User-defined Functions.
Option D is incorrect: The function specifies a user-defined type, requires EXECUTE permission on the type, and not always.
Reference: 
To know more about modifying UDF with ALTER Function, please refer to the doc below: 

https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/modify-user-defined-functions?view=sql-server-ver15#Security