Part A:
The statement that best explains the main argument presented in paragraph 4 of "The Importance of Sending People to Space" is:
C. The cost of human space exploration may seem like it costs more, but it could be worth the expense.
Part B:
The sentence from "The Importance of Sending People to Space" that best supports this answer is:
B. Giving astronauts what they require to stay healthy in space naturally makes these kinds of missions more expensive than ones that use robots.
This sentence highlights the increased cost of human missions while also implying that these costs can be justified by the potential benefits they bring.