Answer:
for transportation
for protection
for access to food
to live off of a host
Step-by-step explanation:
Organisms enter commensal relationship primarily for benefits such as transportation, protection, access to food, habitat, and so on.
Commensalism is a form of relationship between two organisms in which one of them (the commensal) gains some benefits and the other is unaffected in any form.
The benefits a commensal derives from commensalism could be nutritionally, transport, protection or habitat related. E.g the remora and the shark relationship in which the remora attaches itself to the shark and derives its food from the leftover foods of the shark as well as gets transported around in the process.