C Programming Quizzes C Language Function

Question:
Which of the following is a complete function?

Option A):
int funct(int x) { return x=x+1; }
Option B):
void funct(int) { printf(Hello"); }
Option C):
int funct();
Option D):
void funct(x) { printf(Hello"); }

Correct Answer is Option A):
int funct(int x) { return x=x+1; }