In July, a Student Tested the Soil in Two Plots

Multiple Choice

In July, a student tested the soil in two plots and calculated the concentration of nitrogen compounds present in each plot. The student then planted 20 seedlings in the first plot and allowed them to grow. Nothing was planted in the second plot. The student tested the soil in both plots again after one month. The concentration of nitrogen compounds had decreased in the first plot but had remained the same in the second plot. Which of the following best explains the decrease in nitrogen compounds in the first plot?

A) The nitrogen compounds had broken down into elements.
B) The nitrogen compounds were absorbed by the seedlings for their growth.
C) The nitrogen compounds escaped through air pockets created by the seedlings' roots.
D) The nitrogen compounds had evaporated because of the warm summer temperatures.