Task: Question Answering
Input (English): The populations of two species of bacteria in a petri dish vary inversely. If there are 1,000 bacteria of species A when there are 500 bacteria of species B, how many bacteria of species B are there when there are 2,000 bacteria of species A ?
(A)250 (B)500 (C)750 (D)1,000 (E)2,000
Output (English): A