In active transport:
a. molecules move across the plasma membrane by crossing the lipid bilayer directly, rather than by using a transport protein.
b. the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell.
c. no energy input is required from the cell.
d. a vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell.
e. molecules move across the plasma membrane against their concentration gradient.

The correct option is: e. molecules move across the plasma membrane against their concentration gradient

Explanation:

Active transport refers to the movement of the particles or molecules from higher concentration to lower concentration, across the plasma membrane of a cell. This transport requires cellular energy as the movement of the molecules is against the concentration gradient.

Active transport can be divided into primary and secondary active transport.

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.