Which of the following is a example of moving properly for push up?

Which of the following is a example of moving properly for push up?

A - raising and lowering the body to a 90° angle at the elbow with a flatback. .
B - raising and lowering the body to greater than a 90° angle at the elbow with a flatback.
C - raising and lowering the body to less then a 90° angle at the elbow with a flat back
D - raising and lowering the body with elbows locked out in a position in the flatback