You are given a science question (easy-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 Q]: Which is a way the agricultural biotechnology industry could have a positive impact on the environment?  
 (A) by producing crops that are virus resistant (B) by making robots to replace large farm machines (C) by reducing the need for countries to import food (D) by increasing the use of wind farms that produce electricity
[EX A]: C

[EX Q]: How do most fish get the oxygen they need to survive?  
 (A) They take in water and break it down into hydrogen and oxygen. (B) Using their gills, they take in oxygen that is dissolved in water. (C) They get their oxygen from the food they eat. (D) They come to the surface every few minutes to breathe air into their lungs.
[EX A]: B

[EX Q]: Today's limestone caverns were once solid rock. Acidic rainwater seeping through the rock over hundreds of years dissolved part of the rock, forming caverns. This is an example of  
 (A) erosion. (B) deposition. (C) physical weathering. (D) chemical weathering.
[EX A]:
D