Why is A correct? Why is E incorrect?

@Ryan-Mahabir, (E) is a premise used to support the conclusion, whereas (A) is the main conclusion. One way to identify the main conclusion is to try to insert "because" in front of the premise and "therefore" in front of the conclusion. Because most anthropologists underestimate the effect of living in the community although they are aware of the effect. Therefore, usefulness of field studies tend to be overrated by anthropologists.