Task: Question Answering
Input (English): A cricket population includes approximately the same number of black and light-brown crickets. Black crickets are easier for birds to locate and eat. Over time, the population begins to consist of only light-brown crickets. The change in the color of the cricket population is a result of   
 (A) limited resources. (B) natural selection. (C) geographic isolation. (D) climate change.
Output (English): B