Hairy skin

Which one is correct?

(a) The rambutans are hairy fruit.
(b) The rambutans have (many) hairy skin.
(c) The rambutans have many hairy.

(b) and (c) are ungrammatical.

I'd be more inclined to say, "The rambutan is a hairy fruit," or "Rambutans are a hairy fruit."

But your version may be okay.

I'm quite sure we should be using "fruit" in the singular - like, "The mongoose is a strange animal."
Now I'm confused. We wouldn't say "Mongeese are a strange animal." - Or would we?

These questions had been asked more than once before from my recollection.

For sure, the last two sounded atrocious beside ungrammatical.

Even the first one sounds funny. The article is not neccesary and singular makes more sense.

If I say, for example, mango is my favorite fruit, I am talking about one type of fruit, not all the mangos as in plural.