Task: Question Answering
Input (English): A plant growing on a hillside has a stem that curves so that the plant is vertical. This curve is not observed in plants of the same species growing on level ground. Which statement best explains the curved stem of the plant growing on the hillside?  
 (A) It is a trait for which the plant has no genes. (B) It is a trait that is usually detrimental to plant survival. (C) It is a trait that developed in response to temperature variations. (D) It is a trait that is only expressed under particular environmental conditions.
Output (English): D