does anyone know how to solve this ?

[Q3] (5 X 4 = 20 points) This question tries to highlight that the intersection of an infinite number of open sets may or may not be open. Similarly, the union of an infinite number of closed sets may or may not be closed. (a) If Sn = (n, n + 1), then prove that OneNJ Sn is both open and closed. (b) If Sn = (-2, 1), then prove that OneN. Sn is neither open and nor closed. (c) If Sn = [-n, n], then prove that UnEN. Sn is both open and closed. (d) If Sn = [n,1 -], then prove that UneN. Sn is open and not closed