for what kind of amplifications can the active region of the common-emitter configuration be used?(a)power(b)current(c)voltage(d)all of these

The active region of the common-emitter configuration can be used for all types of amplifications mentioned. This includes:

(a) Power Amplification: The common-emitter configuration is widely used in power amplifiers because it has both voltage gain and current gain. The product of voltage and current gain gives power gain.

(b) Current Amplification: In the common-emitter configuration, the output current is controlled by the input current, hence it provides current amplification.

(c) Voltage Amplification: The common-emitter configuration is most commonly used for voltage amplification because the output voltage is 180 degrees out of phase with the input voltage, providing a high voltage gain.

(d) All of these: So, the common-emitter configuration can be used for power, current, and voltage amplifications.