Task: Question Answering
Input (English): Sofia put a bat house in a tree in her yard. The bats ate mosquitos in Sofia's yard at night and roosted in the house during the day. Droppings from the bat house nourished the tree. What kind of relationship exists between Sofia, the bats, and the tree?  
 (A) The relationship is competitive. (B) The relationship is cooperative. (C) The relationship is parasitic. (D) The relationship is predatory.
Output (English): B