Critical Reasoning

Psychologists recently conducted a study in which people from widely disparate cultures were asked to examine five photographs. Each photograph depicted the face of a person expressing one of five basic human emotions - fear, happiness, disgust, anger, and sadness. The people in the study were asked to identify the emotion being expressed in each photograph. For each photograph, everyone identified the same emotion. This shows that people are genetically predisposed to associate certain facial expressions with certain basic emotions.

Which one of the following is an assumption on which the argument depends?

(A) For each photograph, the emotion that the subjects agreed was being expressed was the emotion that the person photographed was, in fact, feeling.
(B) One's emotional disposition is not influenced by one's culture.
(C) Some behaviors that are present in people from widely disparate cultures are nonetheless culturally influenced.
(D) If there is a behavior common to people of widely disparate cultures, then there is probably a genetic predisposition to that behavior.
(E) The people whose faces were depicted in the photographs were not all from the same culture.

What's the best approach to determine the answer? Can any experts help? I

This is an LSAT question.

The conclusion of the argument is: People are genetically predisposed to associate certain facial expressions with certain basic emotions.
Why? Because people from widely disparate cultures all successfully identified the emotion portrayed in the photographs regardless of their culture.

What new, surprising word is in the conclusion? A word not mentioned elsewhere in the argument? The word is genetic.

Whenever you find a new word or concept in the conclusion that was not mentioned in any of the premises, that word must tie to the premises through an assumption. Thus, the correct assumption will have the word genetic in it.

Accordingly (D) is our best candidate. But what if we are not convinced by that? What if we want to test it? If so, we can use the negation test.

The negated assumption should damage the conclusion. The negated assumption is: If there is a behavior common to people of widely disparate cultures, then there is probably not a genetic predisposition to that behavior.

As we can see, the negated (D) damages the conclusion. Accordingly (D) must be a necessary assumption on which the argument is based.