How does a programmer distinguish a child from its parent process following a fork system call?

The system call returns 0 to the child and 1 to the parent.

The system call returns 0 to the parent and the pid of the parent to the child.

The system call returns 0 to the child and the pid of the child to the parent.

There is no way to distinguish a child from its parent.

Answer:
The system call returns 0 to the child and the pid of the child to the parent.

Note: This Question is unanswered, help us to find answer for this one