Answer:
What is the effect of vegetarianism on the human body?
Explanation:
The other options, "How many people in the US practice vegetarianism," "Do most vegetarians eat dairy and eggs," and "Can vegetarians wear leather shoes and jackets," are not very good research questions because they can be answered with a minimal amount of research, and it doesn't involve information that is particularly interesting to the reader.
All three of the other answers would probably only require one source in order to answer the question effectively due to their simplicity, and they involve questions that wouldn't really be particularly useful to the reader, and thus not interesting either. However, the question, "What is the effect of vegetarianism on the human body," would be useful and therefore interesting to the reader because it may or may not encourage them to take up vegetarianism themselves, whereas the other questions would just provide statistics and the answers to commonly asked questions.
