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:
The students in a class are making a scale model. They need a material that they can easily bend into a circle. Which of the following objects is best for the students to use?  
 (A) copper wire (B) glass rod (C) lead pipe (D) wooden stick

Ex Output:
A


Ex Input:
Which pair of organisms benefits each other the most?  
 (A) birds building a nest in a bush (B) worms eating the roots of a plant (C) squirrels burying seeds from a tree (D) deer scraping their antlers on a tree

Ex Output:
C


Ex Input:
A lake that received runoff from surrounding farmland had a healthy fish population. Several years ago, a new type of pesticide was used to treat crops. As runoff entered the lake, it killed an insect that was a primary food source for fish. Which will most likely occur if farmers in the area stop using the pesticide?  
 (A) The population of fish will increase. (B) The insects will become more resistant to the pesticide. (C) The lake will be unable to support life. (D) The fish will find another food source.

Ex Output:

A