What initiates an action potential on a muscle cell?
a. acetylcholine binding to receptors on the sarcolemma within the neuromuscular junction
b. acetylcholinesterase
c. myosin cross bridges binding to actin
d. atp?

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.

the correct answer is:

a population changes in response to a change in the environment.