23. A student group is involved in a restoration study of a nearby disturbed area. They decide to collect six soil samples and analyze them for carbon (C) and nitrogen (N). Two of the samples are found to be
very high in C and N, but the other four samples are low in both. The students also notice that the color
of the two soil samples that are high in C and N is very dark. Which of the following is the most likely
explanation of the data?
a. Two of the samples were collected from an A horizon, and the others were collected
from a B horizon.
b. Two of the samples had more sand and gravel than the other four.
Four of the samples were collected from an area that had been restored previously
and now has thick vegetation.
d. Four of the samples were collected from an area that had been mulched.
e. Four of the sample sites had been treated recently with a chemical fertilizer.
C.