Answer:
(a) forward-reverse
Step-by-step explanation:
A transistor is an electronic component which consist three electrodes, base-b, collector-c and emitter-e. It is a semiconductor and some of its types are n-p-n, p-n-p, field effect transistors (FET), bipolar junction transistors (BJT) etc.
For a transistor to function as a linear amplifier, it must be appropriately biased. The major required condition is forward-reverse bias. This ensure the appropriate functioning of the transistor as an amplifier of electronic signals.