Please Use the Following Information to Answer the Question(s) Below

Please use the following information to answer the question(s) below.
A scientist conducts an experiment to quantify the effect of mycorrhizae and soil nitrogen levels on plant growth in a grassland. The experiment has four treatments: (1) Mycorrhizae present and ambient levels of nitrogen, (2) mycorrhizae present and nitrogen added, (3) mycorrhizae absent and ambient levels of nitrogen, and (3) mycorrhizae absent and nitrogen added. After four weeks, the scientist removes the aboveground plant material for weighing. Figure 42.4.
-What is the dependent variable in the experiment shown in Figure 42.4?

A) net primary productivity
B) gross primary productivity
C) net secondary productivity
D) standing crop