(c)
The probability $= P({\overline{A}}_{1} \cap {\overline{A}}_{2} \cap {\overline{A}}_{3} \cap \ldots. \cap {\overline{A}}_{n})$ (none of the events occur)
$= P\left( {\overline{A}}_{1} \right)P({\overline{A}}_{2})P\left( {\overline{A}}_{3} \right)\ldots P({\overline{A}}_{n})$
$= \frac{1}{2} \bullet \frac{2}{3} \bullet \frac{3}{4}\ldots\frac{n}{n + 1}$
$= \frac{1}{(n + 1)}\$
$\therefore$ Probability that atleast one of the events occurs
$= 1 - \frac{1}{n + 1} = \frac{n}{n + 1}$