two ways in which parasites are dependent on their host?

Answer 1

A host provides a parasite with an environment in which it can thrive, with respect to pH and other chemical factors, and is protected from harmful influences like other microorganisms. A host also provides a parasite with nutrition, in that the parasite either consumes food that the host intended for itself, or it directly consumes parts of the host.

Answer 2

Host provide food for the parasite.
They also provide shelter/living environment for them.