Parasitism
Life line a parasite canot exist with out a host.
The relationship between a flea and cat's fur is that of parasite and host. The flea is a parasite that feeds on the blood of the host.
parasite/host
The relationship between the parasite and host is that they share they same body, with the parasite living off the hosts cells and energy etc.
This kind of relationship between host and parasite is called mutualism.
There is none
A shell provides protection and shelter for a hermit crab, which uses it as its home. The hermit crab carries the shell on its back and can move to a larger one as it grows. This symbiotic relationship benefits both the hermit crab and the shell.
Dogs/fleas is an example of a Host/parasite relationship.
Commensalism
yes, because the parasite is taking from the host and the host is not getting anything from it (unless the parasite is taking bad things from the host, which would mean it depends on the species of parasite).
mutalism
the first is a parasite on the 2nd