We have two performance parameters for small$-$signal analysis of BJT$-$based amplifiers. They are $$and $.$ Select all correct options:

a$)$is the amplifier gain from the input voltage to the output voltage.$$

b$)$is the amplifier gain from input voltage to collector current.$$

c$)$is the internal resistance of the external input AC source.

d$)$ Both $$are independent of DC operating points as they are amplifier parameters for AC signals.

e$)$ Both $$are dependent on the choice of DC operating points, although they are amplifier parameters for AC signals.$$