You are given an elementary science question along with a few answer options. List all the words from the question that are essential and sufficient for choosing the correct answer option. Keep in mind that essential words are necessary to understand the meaning of the given question. However, non-essential words provide little information needed to select the correct answer. You can think about it like this: If the question was in another language, knowing the meaning of which words were necessary and enough for you to understand the question and answer it?. If your answer consists of multiple spans of words from the question, separate those using a comma (", "). Do not generate any word that is not present in the question. Make sure that your response is contained in the given question and the words are in the same order as the question.
 Grammatical correctness is not important.

Ex Input:
Question: Infections may be caused by (1) mutations (2) microorganisms (3) toxic substances (4) climate changes?

Ex Output:
Infections, caused


Ex Input:
Question: What happens at the boiling point of a substance? (A) liquid becomes a gas (B) solid becomes a gas (C) liquid becomes a solid (D) solid becomes a liquid?

Ex Output:
boiling, point


Ex Input:
Question: While Anna was testing a circuit, she dropped a light bulb. What is the safest thing Anna can do? (A) get a new bulb to finish the test (B) push the broken glass under a table (C) tell her teacher that she broke the bulb (D) ask her partner to help pick up the broken glass?

Ex Output:

dropped, light, bulb., safest, thing