Which region is the least doped in a transistor?

An $n-p-n$ transistor power amplifier in $C-E$ configuration gives

In the circuit shown in the figure,when the input voltage $V_i$ is $10\, V$,$V_{BE}$ is zero and $V_{CE}$ is also zero. Find the values of $I_B$,$I_C$,and $\beta$.

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:

The current amplification factor of a transistor in common emitter configuration is $80$. If the emitter current is $2.43 \text{ mA}$, then the base current is (in $\mu \text{A}$)

Three terminals of a transistor,denoted by $P, Q,$ and $R,$ are tested using a multimeter. No conduction occurs between $P$ and $Q.$ When the negative lead of the multimeter is connected to $R$ and the positive lead is connected to either $P$ or $Q,$ the meter shows some resistance. Which of the following options is correct for the given transistor?