M Prep | MCAT 2015 Question of the Day - Prep, Practice Questions, and More!

Q:

A researcher has an agar plate covered with a lawn of E. coli. She adds a drop of a unknown substance, and the next day there is a clear spot on the plate where the substance was added. This substance could be:

I. A virus undergoing the lytic cycle.
II. A virus undergoing the productive cycle.
III. A chemical that is toxic to prokaryotes.

A

I only

B

III only

C

I and III only

D

I, II, and III