What is active transport? A. The movement of molecules down a concentration gradients from high to low , using no energy.
B. The movement of molecules up a concentration gradient from low to high , using energy
C. The movement of molecules down a concentration gradient from high to low , using energy
D. the movement of molecules up a concentration gradient from low to high , using no energy

B. The movement of molecules up a concentration gradient from low to high, using energy

Explanation:

In active transport, the molecules move against the concentration gradient.

This means that the molecules move from an area of low concentration to an area of high concentration.

Because it goes against the concentration gradient, it requires the use of ATP energy.

So, B is correct because it is the movement of molecules from a low to high concentration using energy.