Final answer:
A closed chain exercise for the upper extremity is exemplified by the push-up because the hands are stationary and in contact with the ground.
Step-by-step explanation:
The student has asked about an example of a closed chain exercise for the upper extremity. A closed chain exercise is characterized by the movement where the hand (or foot) is in a fixed position, and cannot move freely. This typically involves the extremity being placed against a solid surface or object. With this definition in mind, the correct answer is a. Push-up. During a push-up, the hands are in contact with the ground and remain stationary, while the rest of the body moves in relation to them. This is in contrast to the other exercises listed, such as the military press and bench press, where the hands move freely and are not fixed in position.