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.

Which of the following is the main role of flowers found on most flowering plants?  
 (A) to take in air (B) to produce seeds (C) to absorb nutrients (D) to protect the stem
B

The cells of a plant help the plant maintain its life functions. What part of a plant cell has the function of producing sugar in the presence of sunlight?  
 (A) chloroplast (B) cytoplasm (C) mitochondria (D) nucleus
A

A dark colored wall becomes warm when the Sun is shining on it. After the Sun sets, a person standing a meter away can feel warmth from the wall. How does heat transfer from the wall to the person?  
 (A) radiation (B) conduction (C) convection (D) insulation

A