The correct option is B 192 Hz
As string is vibrating in full segments (loop), then string is fixed at both ends.
Frequency of vibrations is given by
f=nv2l
For same string, f∝n
So, f1f2=n1n2
⇒480f2=52 [1 segment=1 loop]
⇒f2=192 Hz
So, option (b) is correct.