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]: About how long is a lunar cycle?  
 (A) 1 day (B) 1 week (C) 28 days (D) 52 weeks
[EX A]: C

[EX Q]: The parts of plants that make seeds are the  
 (A) roots. (B) stems. (C) flowers. (D) leaves.
[EX A]: C

[EX Q]: Heat from deep in Earth's interior is transferred to its crust by which of the following?  
 (A) conduction in the ocean (B) convection in the mantle (C) radiation from the solid core (D) evaporation at mid-ocean ridges
[EX A]:
B