Amotor unit consists of : a. a motor unit consists of one nerve and all the skeletal muscles it innervates. b. one neuron and all the skeletal muscle fibers it controls. c. one axon terminal branch and the myofibrils it controls. d. one skeletal muscle fiber and all the neurons that control that fiber.

The correct option is A.  a motor unit consists of one nerve and all the skeletal muscles it innervates.

Explanation:

Motor units are involved in functions like controlling the muscle contractions in an organism. A motor unit comprises of a motor nerve which innervates with a number of muscle fibers. For example, in the temporalis muscle, a motor nerve innervates with 1000 fibers.

A number of motor units might work up together in the form of a group to provide contractions to a single muscle. The type of fiber for all the units is same.

d i think its   answer d

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.