Some Aquatic Invertebrates Such as Insects and Snails Feed on Biofilms

Some aquatic invertebrates such as insects and snails feed on biofilms. Scientists that study metal-contaminated streams have documented that some biofilms in stream environments absorb zinc from stream water during daylight hours and release the zinc into the stream during the night. If the scientists were to test exposure of the invertebrates to zinc, what might they hypothesize?

A) The greatest exposure to aquatic invertebrates that feed on biofilms might only occur during daylight hours.
B) The greatest exposure to aquatic invertebrates that feed on biofilms might only occur during night hours.
C) Aquatic invertebrates that prefer to feed at night will encounter little exposure to zinc.