Let us define an interval $A(n)$ as a function of $n$ as $A(n)=(-1 / n, 1 / n)$. Then the set of points that lie in the intersection of $A_{n}{ }^{\prime} s, n=1, \ldots, \infty$
- is an interval
- is a single point
- is an empty set
- cannot be determined
- has two disjoint intervals