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]: When microorganisms deplete the oxygen in soil through respiration, the soil becomes  
 (A) humus. (B) anaerobic. (C) compost. (D) aerobic.
[A]: B


[Q]: Some events on Earth happen instantly while others take thousands of years to occur. Which process takes the longest time to complete?  
 (A) rivers rising due to storms and floods (B) evaporation of water from the leaves of a plant (C) weathering of a rock to form small rocks and sand (D) movement of small pieces of rock by flowing water
[A]: C


[Q]: The praying mantis is well camouflaged in its natural habitat. What is a benefit of this adaptation?  
 (A) It increases the mutation rate of favorable genes. (B) It reduces the risk of being eaten by a predator. (C) It allows absorption of chlorophyll from plants. (D) It improves the chances of finding a mate.
[A]:
B