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


question:
Question: Kyle designed an investigation to see if the number of earthworms increased in the soil next to his house. How should he begin his investigation? (A) Count the number of earthworms that are already there (B) Make sure that there are no other organisms located in the soil (C) Clean out the plants in the garden (D) Make sure that the soil is moist?
answer:
investigation, earthworms, increased, soil, begin, investigation?


question:
Question: A science class is taking a field trip to a forest to observe and study birds. Which tool would be most helpful for observing birds? (A) beakers (B) binoculars (C) safety goggles (D) microscopes?
answer:

tool, observing, birds?