Which of these is a unipolar transistor?

In a common base circuit of a transistor,the amplification factor is $0.95.$ The base current when the emitter current is $2\,mA,$ is ....$mA$

In an $N-P-N$ transistor circuit,the collector current is $10 \ mA$. If $90\%$ of the electrons emitted reach the collector,then the emitter current $(I_E)$ and base current $(I_B)$ are respectively:

$A$ common emitter transistor amplifier has a current gain of $50$. If the load resistance is $4 \ k\Omega$ and input resistance is $500 \ \Omega$, the voltage gain of the amplifier is

$A$ transistor is operated in common emitter configuration at $V_C = 2 \, V$ such that a change in the base current from $100 \, \mu A$ to $300 \, \mu A$ produces a change in the collector current from $10 \, mA$ to $20 \, mA$. The current gain is

In the symbol of a transistor,the arrow indicates the direction of: