"up-regulation involves the loss of receptors and prevents the target cells from overreacting to persistently high hormone level"a. trueb. false

The above statement is false.

Explanation:

During up-regulation a cell tends to increase its number of receptors. During down regulation, loss of receptors takes place.

During up regulation the cell tends to become more sensitive to a particular hormone. Up-regulation occurs when the concentration of a hormone is very little. This method is useful because when the concentration of a hormone are less, increasing the hormone receptors increases the chances of the cell to interact with the hormone.

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.