Lexi's teacher gave each person in the class several cotton swabs to test for bacteria on surfaces of various objects. Lexi tested many objects like the pencil sharpener, the dry-erase board, the doorknob, and the overhead projector. She found that the doorknob on the outside of her classroom had more bacteria than any other tested object. Which of the following questions would best help Lexi find out more information about the doorknob's bacteria? A. What color is the doorknob? B. What are the sources of the bacteria? C. Is the doorknob bigger than the other objects? D. What does the doorknob look like?