The best answer is B. The researchers’ hypothesis is “that anteaters use electroreceptors to detect electrical signals given off by prey.” Evidence that electrical signals emanate from the nesting chamber of an ant colony-on which anteaters are known to prey-would strengthen the hypothesis.
Choice C may actually weaken the hypothesis: the passage implies that the rapidity with which anteaters were able to locate ants’ nesting chambers suggested to researchers that anteaters were using electroreceptors to locate prey.
Choice A and D provide evidence that does not strengthen the hypothesis.