Define a function f ∶ ℝ → ℝ by
f(x)= \(\begin{cases}\cos (2\pi/\rm x) & \text { when } \rm x \neq 0 \\ 0 & \text { when } \rm x=0\end{cases}\)
On which of the following subset of ℝ, the restriction of f is a continuous function?
1
(−2, 2)
2
{2/n ∶ n ∈ ℕ}
3
(0, 2)
4
none of the above