Between the function’s . . . . . . . . and . . . . . . . . you enter the instructions to process when the function is invoked.

The correct answer is: A. Header and footer

A function is a block of code that can be called repeatedly. It has a name, a set of parameters, and a body. The header of a function contains the name of the function and the type of its parameters. The footer of a function contains the return statement, which returns the value of the function.

The instructions to process when the function is invoked are entered between the header and footer of the function. These instructions are called the body of the function.

Here is an example of a function:

def add_numbers(x, y):
"""Adds two numbers."""
return x + y

In this example, the function add_numbers takes two parameters, x and y, and returns their sum. The body of the function is the code between the header and footer.

Here is an example of how to call the function add_numbers:

>>> add_numbers(1, 2)
3

In this example, the function add_numbers is called with the arguments 1 and 2. The function returns the value 3.

I hope this helps! Let me know if you have any other questions.