You Perform an Experiment in Which You Take 16 Pots

You perform an experiment in which you take 16 pots of strawberry plants and give half of them 1 gram of ammonium nitrate per liter of water and the other half just get water. Each group is then split in half again, and exposed to either 8 or 16 hours of light each day. You monitor the height of the plants for four weeks. You observe that increasing ammonium nitrate and light both increase plant height.
-In this experiment,the molecule ammonium nitrate is acting

A) on the cells of the strawberries, but with no evidence of impacts on tissue scale of the strawberries being grown.
B) only on the molecular scale of life in the strawberry plants.
C) with uniform responses of growth by all sixteen strawberry plants observed-a standardized variable.
D) on the molecules, but also producing responses at the cell, tissue and organism scales of the strawberries.
E) on the naturral ecosystem scale of strawberry plants, as they are grown from seeds.