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 material best conducts heat and electricity?  
 (A) metal (B) plastic (C) rubber (D) wood
[A]: A


[Q]: A scanning electron microscope is best suited for observing  
 (A) diffraction of light. (B) tectonic features on planets. (C) the surfaces of small objects. (D) topographical features on the ocean floor.
[A]: C


[Q]: Which of these living things in a grassland ecosystem depend on the presence of a variety of bacteria and other microorganisms in the soil?  
 (A) worms only (B) green plants only (C) plants and animals only (D) all the organisms in the ecosystem
[A]:
D