You will be given a definition of a task first, then some input of the task.
In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").

Chimpanzees dig for insects with sticks; what is another example of using tools? (A) birds using twigs to build nests (B) otters using rocks to open clams (C) anteaters using their tongue to catch ants (D) koalas using their pouch to hold infants
Output:
B