Pleased answer this easy riddle I already know the answer but please answer it.

Please answer without any help of app or family and friends.

What is present in a CALL but not in a BALL;
It is present in a WELL but not in a WALL;
And mostly it is seen twice in ALL.

I'LL MARK YOUR ANSWER BRAINLIEST IF IT IS THE CORRECT ANSWER..

GOOD LUCK.<3​