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.

The body is made up of many systems that interact with one another. For example, the skeletal system and the muscular system work together to help the body move. Which system works with the respiratory system to distribute oxygen to the body?
(A) muscular system (B) digestive system (C) lymphatic system (D) circulatory system
D

A student examines a new watch design. The watch has a small solar cell on its face. The main function of the solar cell is to
(A) reduce the cost of the watch. (B) provide an energy source for the watch. (C) make the watch more attractive. (D) stop the watch from speeding up.
B

Why is the particular sequence of bases in a segment of DNA important to cells?
(A) Some base sequences code for protein production. (B) Some base sequences cause the release of lipids from the nucleus. (C) Some base sequences contain the order of sugars in polysaccharides. (D) Some base sequences produce electrical signals sent to the cytoplasm.
A