Answer:
Defend and challenge are pretty much the opposite of each other here. To defend an argument is to persuade others why the argument is sound. To challenge an argument means you are arguing against IT.
Explanation:
The sentence "Moreover, it is probably just as valuable or more valuable to us now, than it was in the ancient past".
I know without a doubt that i should drink more water after exercising would most likely be your answer.
I think its romance in clam, because it talks about love in nature