The correct answer is: C. Both npn and pnp BJT.
A BiCMOS inverter is a type of logic gate that uses both bipolar junction transistors (BJTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). The BJTs are used to provide high current gain, while the MOSFETs are used to provide low power consumption.
In a BiCMOS inverter, the input signal is applied to the base of the npn transistor. The collector of the npn transistor is connected to the load, and the emitter of the npn transistor is connected to the ground. The base of the pnp transistor is connected to the output of the inverter, and the collector of the pnp transistor is connected to the power supply. The emitter of the pnp transistor is connected to the load.
When the input signal is high, the base of the npn transistor is turned on, and current flows from the collector to the emitter. This current flows through the load, turning it on. When the input signal is low, the base of the npn transistor is turned off, and current does not flow from the collector to the emitter. This causes the load to turn off.
The advantage of a BiCMOS inverter over a CMOS inverter is that it can provide higher current gain. This allows the BiCMOS inverter to drive larger loads. The disadvantage of a BiCMOS inverter is that it consumes more power than a CMOS inverter.
Option A is incorrect because only npn BJTs are used in a BiCMOS inverter. Option B is incorrect because only pnp BJTs are used in a BiCMOS inverter. Option D is incorrect because a multi emitter npn BJT is not used in a BiCMOS inverter.