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]: Earth is composed of layers of material with different properties. Which of the following is most likely to be in constant motion?  
 (A) core (B) mantle (C) oceanic crust (D) continental crust
[A]: B


[Q]: Why does the leaf of a plant look green?  
 (A) Because it absorbs green light (B) Because it reflects green light (C) Because it absorbs only yellow and blue light (D) Because it reflects a mixture of yellow and blue light
[A]: B


[Q]: Which technology enables doctors to monitor the function of the heart?  
 (A) dialysis machine (B) electrocardiogram (C) electroencephalogram (D) automatic external defibrillator
[A]:
B