Custom function definitions:. A. Must be written before they are called by another part of your program
B. Must declare a name for the function
C. Must include information regarding any arguments (if any) that will be passed to the function
D. all of the above

D. all of the above

Explanation:

A option is correct and function definition must be written before they are called by another part of your program. But in languages such as C++ you can write the prototype of the function before it is called anywhere in the program and later write the complete function implementation. I will give an example in Python:

def addition(a,b): #this is the definition of function addition

    c = a + b

    return c    

print(addition(1,3)) #this is where the function is called

B option is correct and function definition must declare a name for the function. If you see the above given function, its name is declared as addition

C option is correct and function definition must include information regarding any arguments (if any) that will be passed to the function. In the above given example the arguments are a and b. If we define the above function in C++ it becomes: int addition( int a, int b)

This gives information that the two variables a and b that are parameters of the function addition are of type int so they can hold integer values only.

Hence option D is the correct answer. All of the above options are correct.