The argument starts by stating that people have positive or negative responses to certain words. We are then told that experiments show that people have similar responses to nonsense words. The author then says that experiment shows that peoples' responses to words are conditioned by how the words sound.
The final sentence is the conclusion of the argument. The "This shows" is often a giveaway for a conclusion.
The question asks us what role the result of the experiment (second sentence) plays in the argument. Since the conclusion is that peoples' responses to words are conditioned by how they sound, we can probably think that the result of the experiment supports this conclusion- since someone responding to a word with no meaning suggests they are responding to how that word sounds.
(A) Is wrong as the conclusion of the argument is not that people have a response to any word (B) Is wrong because the statement is not a conclusion. There is nothing offered in support of it. (C) Is wrong because there is no real connection between the statement and the claim that meaningful words can trigger positive or negative responses. (D) Matches what we expected, as the statement is a premise, and it supports the conclusion. (E) Is wrong as the statement is not a conclusion.