Answer is:
option4
\( 29 \)
Solution:
The series
\[
\sum_{n=1}^{\infty}\frac{1}{n^{a-27}}
\]
is a \(p\)-series with
\( p=a-27 \).
Such a series converges only if
\( p>1 \).
Hence we must have
\[
a-27>1
\]
Thus
\[
a>28
\]
The least integer value that works is
\[
a=29
\]
