Answer :

1. Mutualism is a type of relationship that can be seen between two individuals of two different species to obtain benefits for both of individuals.

Examples : Coral polyps and zooxanthellae
                   bee and flower
                   Lichens
                   Rhizobium and root nodules
                   Ungulates and bacteria which live in their intestines

2. Commensalism (this is the correct word) is a type of relationship between two organisms which belonged to two different species that one individual obtains benefits while other doesn't have any harm or benefit.

Examples : Remora and sharks
                   Orchids and trees
                   Pseudoscorpions and Beetles
                   Cattle Egrets and Livestock
                   hermit crab and sea anemone

3. Parasitism is a relationship between two organisms of two different species where one individual (parasite) gets benefits by harming other individual (host).
 
Examples : Cuscuta (parasite) and angiosperms (host)
                    Parasitic viruses (parasite) and human (host)
                    Tape worms (parasite) and pigs (host)
                    Flukes (parasite) and human (host)
                    Parasitic bacteria (parasite) and human (host)