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.

Question: Infectious diseases are caused by (1) allergies (2) vitamin deficiencies (3) chemical spills (4) microorganisms?
Infectious, diseases, caused

Question: An ecosystem is best described as having ___. (A) nonliving factors, only (B) living factors, only (C) living and nonliving factors (D) physical factors, only?
ecosystem

Question: Two objects of different temperatures are touching each other inside a closed room. After a while, they both became the same temperature. In which direction did the transfer of heat move? (A) The heat moved in both directions. (B) The cold moved from the cooler object to the warmer one. (C) The heat moved from the warmer object to the cooler one. (D) Heat transferred from the surrounding air into both objects.?

Two, objects, different, temperatures, touching, inside, room., temperature., direction, transfer, heat