Is the following statement true?
$A\subseteq\mathbb{R}$ closed $\iff$ A is the intersection of a countable collection of closed intervals
For $\impliedby$:
Suppose A is the intersection of a countable collection of closed intervals. The intersection of finite or infinite number of closed sets is closed. So A must be closed.
For $\implies$:
If A is closed, then it can be written as the intersection of arbitrarily many closed intervals. I am not sure if this means that the collection is countable though.
The intersection of any collection of closed intervals is either empty or a closed interval. (Just verify that if two points belong to the intersection then any point between these two is also in the intersection). Hence the stated result is false.