How many times does the electron go around the first orbit of hydrogen atom in one second?

The correct option is D $6.59\times {10}^{15}$
Number of revolutions per second $=\frac{\text{v}}{2\pi r}...\left(i\right)$
In case of Hydrogen atom, (Z = 1, n = 1) $\text{v}=\frac{2.188\times {10}^8}{n}\text{cm/sec}$
$\text{v}=\frac{2.188\times {10}^8}{1}\text{cm/sec}$

$r=n^2\times 0.529\stackrel{\circ }{\text{A}}$
$=1^2\times 0.529\times {10}^{-8}\text{cm}$

$\therefore$ Number of revolutions per second (from eq. 1) $=\frac{2.188\times {10}^8}{2\times 3.14\times 0.529\times {10}^{-8}}=6.59\times {10}^{15}$