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.
--------
Question: A potential negative impact of building a dam on a river is that the dam   
 (A) prevents sediment from flowing downstream. (B) increases the amount of water available to farms. (C) prevents seasonal downstream flooding. (D) increases the rate of water loss from a lake.

Answer: A


Question: 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

Answer: C


Question: Energy companies often produce electricity from a variety of sources. Using which resource would improve air quality the most?  
 (A) oil (B) gas (C) coal (D) wind

Answer:
D


