When an animal evolves to look like a plant, what is that adaptation called?

An adaptation is  a  mutation or genetic change, that helps an organism such as a plant or animal survive in its environment. 

Iam not sure but to me it with be a or dsorry if i was late! hope this ! : )if you really want me to find out the answer that is correct tell me and i will do more research but the a or d makes sense to me.