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.

Q: Which characteristic of sound makes it possible for bats to fly in the dark without hitting any objects?  
 (A) refraction (B) reflection (C) conduction (D) amplification

A: B
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Q: Estuaries are marine environments located in areas where fresh water from rivers flow into the ocean. Estuaries are one of the most biologically productive ecosystems. Birds, fish, turtles and many other organisms inhabit these ecosystems. Which will most likely cause changes to estuary habitats on a global scale?  
 (A) decreases in powerful hurricanes (B) decreases in volcanic eruptions (C) increases in earthquakes (D) increases in sea level

A: D
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Q: The basic life functions of an organism are carried on by  
 (A) cells (B) nutrients (C) atoms (D) hormones

A:
A
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