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.

e, molecules move across the plasma membrane against their concentration gradient.

Explanation:

It is called active transport because it needs energy input from the cell, thus being 'active.'

The reason the cell needs to put in energy is because it moves up against the gradient, which requires energy. It's like swimming upstream rather than following the currents.

answer: c

explanation:

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.