Which of the following is an example of moving properly for a push-up
a. raising and lowering the body to 90° angle at the elbow with a flat back
b. raising and lowering the body to greater than 90° angle at the elbow is a flat back
c. raising and lowering the body to less than a 90° angle at the elbow with a flat back
d. raising and lowering the body with elbows locked out in the up position and a flat back