SAT writing question from January test?

Test Preparation SAT Preparation
1

<p>This is a question I was stuck on from the writing section:</p>

<p>There (has been) a drop (in) the amount (of krill and plankton), a major food supply (for) fish. (No Error)</p>

<p>I put D, "for" because I thought that it should be of. However, I am unsure of this. Could anyone please help me with this? Much appreciated :)</p>

2

<p>Might be A because i think it should be have been</p>

3

<p>in for quantity.</p>