Which of the following is true?

A$.$ A function must have exactly one return statement, or no return statement at all.

B$.$ A function must always have at least one return statement.

C$.$ A function can only return strings and numbers, not lists or dictionaries.

D$.$ A function can have any number of return statements, or no return statement at all.

B$.$ y $=$ calc$\_$sum$()$

C$.$ y $=$ calc$\_$sum$(4+5)$

D$.$ y $=$ calc$\_$sum$(4,5)$