When would a cell use Active Transport? Mark all that apply. a. When the cell needs to move a compound down its concentration gradient.

b. When the cell needs to move a compound against its concentration gradient.

c. When the cell needs to move a polar compound.

d. When the cell needs to move a nonpolar compound.

e. When the cell needs to move an ion.

Option B, When the cell needs to move a compound against its concentration gradient.

Explanation:

A cell uses active transport when it has to transport substances against the concentration gradient across its membrane.

In active transport additional energy is used (generally provided by energy molecules like ATP) to push the substance across any membrane from low concentration side  to high concentration side.

Option B is correct

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.