Scenario that is best researched using a sample survey is
D. A school cafeteria is changing its salad bar. What types of salad items do students in the school prefer?
Explanation:
The question What types of salad items do students in the school prefer? implies that there must be a poll in which the opinion of all students that study in the school must be taken into account before the decision is made.
A survey test is thus the most useful part here as it would take the sample and get their opinion according to which the decision can then be taken by the authorities regarding which salads should be kept in the new cafeteria.