Which one of the following does not contain calories?
a. carbohydrate
b. alcohol
c. water
d. protein

Answer is active transport. Plants use active transport during the ion uptake.

Explanation:

In the process of active transport, substances are moved from an area where they are in lower concentration to a region where they are in higher concentration (against a concentration gradient). The concentration of minerals like magnesium ions is higher in the root-hair cells of plants than in the soil. So the plants take in the ions they need from the soil by the active transport across the root hair cells. This process requires energy which is supplied in the form of ATP (adenosine triphosphate).