To prevent taking back in the wastes it has just expelled,a standard sediment-inhabiting bivalve mollusk should position itself
A) with the incurrent siphon upstream.
B) with the excurrent siphon upstream.
C) in any direction, since it can control which way the water flows in either siphon.
D) either with the incurrent siphon upstream or with the excurrent siphon upstream, but not in any direction, since it can control which way the water flows in either siphon.
E) None of the choices are correct

Question

Quizplus · Accepted Answer

To prevent taking back in the wastes it has just expelled, a standard sediment-inhabiting bivalve mollusk should position itself with the incurrent siphon upstream. This is because the incurrent siphon is the opening through which water enters the mollusk's body, and the excurrent siphon is the opening through which water exits the mollusk's body. If the mollusk were to position itself with the excurrent siphon upstream, it would be taking back in the wastes it has just expelled.

To Prevent Taking Back in the Wastes It Has Just