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.

[EX Q]: Which of these best describes a change that is physical?  
 (A) yarn being knitted into a sweater (B) the engine from a tractor being started (C) the metal on a bicycle forming rust (D) grass capturing the energy from sunlight
[EX A]: A

[EX Q]: Elephants on the African savanna eat shrubs and small trees. This behavior clears land and enables grass to grow. Grazers such as gazelles eat the grass. Lions prey on the gazelles. Which two organisms in this scenario are in the most cooperative relationship?   
 (A) the elephants and the shrubs (B) the shrubs and the lions (C) the elephants and the gazelles (D) the gazelles and the lions
[EX A]: C

[EX Q]: Which of the following is a function of the motor neurons in the nervous system?  
 (A) to directly apply force to the skeletal system (B) to gather information about the stimuli (C) to transmit messages from the brain to the body (D) to directly control the action of muscles
[EX A]:
D