You are given a science question (hard-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.

Electric circuits provide energy for lightbulbs. Which of these prevents the flow of electrons?  
 (A) a circuit that is closed (B) a series circuit (C) a circuit that is open (D) a parallel circuit
C

A student is investigating different types of trees. Two trees are found to have similar growth rates, temperature ranges, and sizes, but different leaves and flowers. The trees are most likely in  
 (A) the same species. (B) the same genus. (C) a different kingdom. (D) a different phylum.
B

Which of these illustrates that sound waves can travel through two different types of media?  
 (A) talking to someone under the water in a pool (B) hearing a loud whisper from across the room (C) hearing people talking on the other side of a wall (D) hearing thunder from a very distant storm

C