In the given block diagram of an op-amp. What are A, B, C and D?

• A. A = Dual input and balanced output differential amplifier, B = Dual input and unbalanced output differential amplifier, C = Level shifter, D = Power amplifier
• B. A = Dual input and balanced output differential amplifier, B = Dual input and balanced output differential amplifier, C = Dual input and unbalanced output differential amplifier, D = Normal amplifier
• C. A = Dual input and unbalanced output differential amplifier, B = Dual input and balanced output differential amplifier, C = Voltage regulator, D = Power amplifier
• D. A = Normal amplifier, B = Dual input and unbalanced output differential amplifier, C = Level shifter, D = Dual input and balanced output differential amplifier