Adam is writing a research paper about recycling, and he has several potential research questions. which is his best option? how many us cities have recycling programs? why didn’t people start recycling earlier in history? what are the effects of recycling on the environment? which materials are recyclable?

The correct answer is C. What are the effects of recycling on the environment?

Explanation:

A research paper is a type of academical formal paper to report the findings and process of researching which is guided by the main question. In terms of the research question, this should be an open question (yes/no questions are not appropriate), it should focus on the topic provided if any and the question should be broad which means the question should explore the topic deeply and multiple sources and concepts are needed to answer it. Considering this, the best question in this case is "What are the effects of recycling on the environment?" because this question addresses the general topic "recycling" but also it is a broad question as it is necessary to gather a lot of information to answer this question and it is the also the only one that would help Adam to understand the topic deeply.

i don't know sorry i cannot read a novel in 30 min.

explanation:

but just in case i think the answer is b.