I believe the correct answer is B. Detrital
The nucleus because it is the brain of the cell, it's what controls it.
Basically, there is a presentation of types of food and the amount of those foods over 50 years in this graph. This means the graph is showing amounts of certain foods over the time period. I'm guessing that basing off of the the previous text you're just noting a change in the breaks of birds based off of the diet available to them at certain times. The adaptations and natural selection will explain the changes because due to certain limited and available foods the diet of the birds change.
Common mistakes and misconceptions
Natural selection is a mechanism, or cause, of evolution. Adaptations are physical or behavioral traits that make an organism better suited to its environment. Heritable variation comes from random mutations. Random mutations are the initial cause of new heritable traits.
A. Looks like the mesophyll of a leaf or a section of it
B. Is the stem
C. Is the surface of the leaf
(I don’t really have any vocab so I can get an exact answer)