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 of the following compounds is most likely to be part of living organisms?
(A) C?H??O? (B) BF? (C) MoCl? (D) CsI
[EX A]: A

[EX Q]: One type of animal hatches from an egg, breathes through gills when it is young, and mainly lives on land as an adult. Into which group is this animal classified?
(A) amphibians (B) birds (C) mammals (D) reptiles
[EX A]: A

[EX Q]: What two factors determine the location of an electron around the nucleus of the atom?
(A) speed and direction of the electron (B) size of the electron and the neutron (C) direction and strength of the electron (D) energy and the attraction of the nucleus
[EX A]:
D