You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Ex Input:
A student plants rosebushes in her front yard. The student is frequently seen pulling weeds from the base of the rosebushes. What is the most likely reason that the weeds are pulled?  
 (A) Weeds add fertilizer to the soil. (B) Weeds use nutrients the roses need to grow. (C) Weeds increase the bacteria in the soil. (D) Weeds consume most of the oxygen.

Ex Output:
B


Ex Input:
Which situation would affect an organism's niche in a positive way?  
 (A) a decrease in livable habitat (B) a decrease in the normal temperature (C) an increase in the amount of prey available (D) an increase in the amount of competitors for food

Ex Output:
C


Ex Input:
Many scientists think that burning fossil fuels has increased the amount of carbon dioxide in the atmosphere. What effect would the increase of carbon dioxide most likely have on the planet?  
 (A) a cooler climate (B) a warmer climate (C) lower relative humidity (D) more ozone in the atmosphere

Ex Output:

B