Ace the LSAT 2025 – Master the Law School Entry Test with Style!

In the argument, the statement that zooplankton feed upon phytoplankton is used as evidence to support a certain claim. This evidence helps to establish a link between zooplankton and phytoplankton, providing support for the main point or conclusion being made in the argument. Therefore, the correct choice is D - Evidence.

Option A, assumption, is incorrect because the statement about zooplankton feeding upon phytoplankton is presented as a factual piece of information rather than an assumption. Option B, counterargument, is incorrect as this statement does not directly oppose or contradict the main point of the argument. Option C, conclusion, is also incorrect as the statement is not the main point that the argument is trying to prove.