First discovered several years ago in North American lakes and rivers, the northern snakehead is a nonnative fish with no local predators. To keep the northern snakehead's population from growing, for the past three years wildlife officials have been paying recreational fishers for each northern snakehead they catch. In this way, the officials hope to stop the northern snakeheads from eliminating rare native fish species.

To evaluate the likelihood that the wildlife officials' plan will succeed, it would be most useful to determine which of the following?

A. Whether the northern snakehead's population in local lakes and rivers could be reduced by introducing predators from its native habitat
B. How local population numbers of rare native fish species have been changing since the wildlife officials started paying recreational fishers to catch northern snakeheads
C. Whether the fish species on which the northern snakehead preys in regions to which it is native and in which it is abundant have become significantly depleted in recent decades
D. What total number of northern snakehead have been caught by recreational fishers since the wildlife officials began paying for them
E. Whether rare native fish species in the region face any threats to their survival other than the proliferation of northern snakehead

OA B

Source: Official Guide