I'd go with A or C. Definitely not B or D.
Answer:
a. Genes are taken from bacteria, and those genes are inserted into corn.
Explanation:
This is an example of TWO clauses (sentences) being brought together by a comma.
Answer:
Service benefits the helpers and those helped.
Explanation:
The whole article talks about how service helps not only the community, but the people that do the service.
