The correct answer to this question is B. Adenine is a compound. The formula for it is C5H5N5. We would use this formula to identify the associating correct label. Labels A, D, and E have no C, automatically eliminating them as the right answer.
While name C has C and H, it has no N. The only solution left that has all three parts of the formula is label B, making it the obvious answer. This question deals with the study of physics and would be found on a test for physics, as well as a knowledge test, such as SATs or an IQ test.