Audio is recorded in frequency = 44.1 KHz
While converting to Mp3 16 bits are used to represent one sound signal.
For sake of stereo 2 channels are used.
Hence
2 channels of 16bit audio at 44.1KHz = 2 x 16 x 44,100 = 1,411,200 bits/sec, or 172kbyte/sec
Compression is made at128kbit, or 16kbyte/sec
So, 172 / 16 = 10.75:1 compression
Ans is D