What are the three required sets of statements for every function that a programmer writes in C plus plus?

Answer 1

There is no requirement for any statement in a C++ function, let alone three sets of statements. For instance, the following is a perfectly valid function:

void foo(){}

Clearly this does nothing as it has no statements in the function body, but it is nevertheless a valid function.

Perhaps you mean something else by "statements". The only requirement of a function is that it have a return type, a valid name, an argument list and a function body. The return type may be void, of course, and the argument list may be empty, but it must include the ellipses. The function declaration need not include the function body, and the argument list need only specify the type of argument (the argument names are optional and need not match those declared in the actual definition).

The function name and the arguments define the function signature (the prototype), thus the three required "components" of a function are the return type, the signature and the function body.