Sharon wishes to identify the food items that are purchased most frequently in the student cafeteria, and, for the purpose, she observes the students' purchasing patterns. This scenario exemplifies the goal of science to:

A. describe behavior
B. predict behavior
C. determine the cause of behavior
D. explain behavior

Describing behavior of any event or person is doen through observation technique .Observing the pattern of something helps in understanding and analyzing act or thought that is taking place in the scenario.

According to the question, Sharon is using behavior description to determine the pattern of food purchase in cafeteria through observing and understanding.

Other options are incorrect because predictive behavior, explanation of behavior and behavior causes are not the factors represented through question's scenario as per goal of science.Thus, the correct option is option(A).