In any problems that require you to draw a conclusion, you are only supposed to use the information provided in the passage to draw a conclusion, nothing more.
A) Read the first sentence. It says that parasitic wasps lay their eggs in EXACTLY THE RIGHT NUMBER. Although worded somewhat awkwardly, this choice is a possibility so I would leave it open.
B) The passage does not mention anything about a host's defenses. Eliminate.
C) The passage does not mention anything about experience. Eliminate.
D) The passage does not mention anything about time. Eliminate.
E) The passage does not mention anything about clues. Eliminate.
This is how I would get to A. CR is a real pain in the ass sometimes b/c the correct answer choice may be difficult to decipher. Sometimes one of the choices may seem like the right answer, but if you examine it closely and it's questionable then it's probably incorrect. Hope this helps.