$P\, (\text{any pair share same birthday})$ = $365*(\frac{1}{365^2})$
$E[(a,b)]=\begin{cases} 1 & \text{ if a and b share same birthday}\\ 0& \text{ otherwise } \end{cases}$
$\text{There are}\;\binom{n}{2}\; \text{pairs in total.}$
$\text{Now, according to the question}\;\; \frac{n(n-1)}{2}*\frac{365}{365^2}\geq 1$
$\text{So, minimum value of}\; n\; \text{would be 28. (because, }28*27 = 756>730\text{)}$
$\text{So, the answer is option }\textbf{B}\;.$