Quick PLEASE will mark brainliest

The first one

Explanation:Parasites increase in the host's body because they need to reproduce, causing the number of parasites to increase

The first one is correct because hosts are usually bigger than the parasite, allowing multiple parasites to thrive in or on a single host, like many ticks on one dog or many cat fleas on one cat, the ticks and fleas being the parasites and the dog and cat being the hosts.

its 42

i say its d?

but there is no

i guess you forgot putting it.