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

The best option of research question according to the theme selected by Adam is C) What are the effects of recycling on the environment? This question can give him a broad field of research and provide a very interesting and high-quality paper with his findings.

6. true

hiv/aids are in fact really common in blood types

yes the first one is correct .