Which term names the group of organisms able to interbreed and produce fertile offspring?

Species

Explanation:

Species is the group of organisms able to interbreed and produce fertile offspring.

Let's break down each word in the question:

"Organisms" means living thing. It can be a plant or animal like we usually think of, but it also includes the really small single-celled living things like some bacteria.

"Interbreed" means to mate with each other.

"Fertile" means that the living thing can also have babies.

"Offspring" means the children that are born.

"Fertile offspring" means that the children that are made must be able to have babies of their own. For example, if a frog and a bird could interbreed, they might produce offspring (children). But, if those frog-birds cannot also have children, then frog-bird is not a species.