What Type of Muscular Activity Is Present in a Muscle

What type of muscular activity is present in a muscle at rest?

A) There is no activity.
B) There is some activity that causes the muscle to make continual tiny movements.
C) Motor units activate partially in a unified wavelike motion.
D) Motor units activate in a random pattern to cause slight constant tension, known as muscle tone.
E) There are large amounts of short contractions.