The correct answer is: A. a called function.

The main() function is the first function that is executed when a program is run. It is called by the operating system. The main() function is typically used to initialize variables, call other functions, and process user input.

A calling function is a function that calls another function. The main() function is a calling function because it calls other functions, such as the functions that initialize variables and process user input.

A recursive function is a function that calls itself. The main() function is not a recursive function because it does not call itself.

The main() function is not used at the end of the program. It is used at the beginning of the program.

Here is a simple example of a main() function:

“`c

include

int main() {
printf(“Hello, world!\n”);
return 0;
}
“`

This program prints the message “Hello, world!” to the console. The main() function is called by the operating system, and it calls the printf() function to print the message. The main() function then returns the value 0 to the operating system.