Which of the following is true for a metric space?

Question

Let $(X,d)$ be a metric space. Which of the following is possible?

1. $X$ has exactly 3 dense subsets.

2. $X$ has exactly 4 dense subsets.

3. $X$ has exactly 5 dense subsets.

4. $X$ has exactly 6 dense subsets.

I've absolutely no clue as to how to tackle this problem.