The correct option is (c) 60dB
Explanation: The total gain of a difference amplifier is the sum of the multiple stages when the gain is calculated is decibels. Given, AV1 = 10dB, AV2 = 20dB and AV3 = 30dB
AV = AV1 + AV2 + AV3 = 10dB + 20dB + 30dB = 60dB