Categorize each relationship as mutualism or parasitism

The question is unclear, is there more to it?

I cannot answer this question without knowing the circumstances, but it is good to remember that mutualism is where both species and/or participants benefit, and parasitism is where one species benefits and the other one is harmed.

Think of mutualism like the word mutual, so when people say " the feeling is mutual" it means that both parties feel and/or express the same feelings. Parasitism should be thought of like a parasite. When one is infected or has contracted a parasite, the parasite will live off of its host body making it ill or even causing death as it drains resources from its host to benefit itself.

the answer is b.) hydrogen bonds between bases.