For a transistor to be used as an amplifier,which of the following conditions must be satisfied?

For a transistor in the active region:
$(a)$ Base,emitter,and collector regions should have similar size and doping concentrations.
$(b)$ The base region must be very thin and lightly doped.
$(c)$ The emitter-base junction is forward-biased and the base-collector junction is reverse-biased.
$(d)$ Both the emitter-base junction and the base-collector junction are forward-biased.
Which one of the following pairs of statements is correct?

In a $CB$ amplifier,the collector current is $5.488 \ mA$ and the emitter current is $5.6 \ mA$. The current gain $(\beta)$ of this transistor will be .......

For a transistor,the current ratio $\beta_{dc}$ is defined as the ratio of:

In a common emitter transistor amplifier,the output voltage and input voltage have a phase difference of

The output characteristics of a transistor are shown in the figure. When $V_{CE} = 10\, V$ and $I_{C} = 4.0\, mA$,then the value of $\beta_{ac}$ is: