Which of these represents an enclave?
a) 1
b) 2
c) 3
d) 5

That would be D

Enclave- A country or part of a country that is within the boundaries of another country.

This could get confused with number 3. Number 3 is not an enclave because it is just on the border of other countries, but number 5 is an enclave because it is surrounded by one whole country. I hope that makes some kind of sense.

Hope this helps :)