ErikaPrepScholar wrote:Whenever we see a comparison work like "unlike", we should start looking for issues of parallelism - comparisons must always compare two parallel things. (An example: "The eyes of sharks are better than fish," does not work because it compares "eyes" to "fish". We need "The eyes of sharks are better than the eyes of fish" or "The eyes of sharks are better than those of fish".)

Here, we have "Unlike the brain of a chickadee that lives in the wild". So we need to be comparing this to another brain - we can predict that we want to compare to "the brain of a caged chickadee". While we don't get those exact words, B does give us:

"Unlike the brain of a chickadee that lives in the wild ..., that of a caged chickadee ..."

Here, "that" is a pronoun that stands in for the subject of the sentence, "brain", just like "those" stood in for "eyes" in our example above. So we are comparing a brain to another brain here. All of the other answer choices do not have parallel comparisons.