Functional groups

Question

1. are the repeating unit of polymers.
2. are groups of atoms whose chemical prop-
erties are pretty much independent of their
chemical environment.
3. perform specific biological functions using
molecular recognition.
4. are a fictitious concept like oxidation
numbers (useful but not real).

Answer 1

And your question is?

Answer 2

It's a multiple choice answer. I need to choose one. I don't know which one, and it would help if there was an answer and explanation to it.