Parasitism
The relationship between a hermit crab and a shell is that thy are mutualism.
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.
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.
parasite/host
This kind of relationship between host and parasite is called mutualism.
parasite
There is none
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).
A relationship in which one organism lives on or inside another organism and harms it is called parasitism. This is a form of a symbiotic relationship.