Here right most non-zero digit depends on the unit digit of $3^{2720}$
$3^{2720}$ = $[3^{4}]^{680}$ =$81^{680}$
The unit digit of 81 is 1 so any power of 81 will always give its unit digit as 1.
Thus, required unit digit is 1.
Hence (1).1 is the Answer.