When an $NPN$ transistor is used as an amplifier,which of the following occurs?

$A$ common-emitter amplifier is designed with a $n-p-n$ transistor $(\alpha = 0.99)$. The input impedance is $1\, k\Omega$ and load is $10\, k\Omega$. The voltage gain will be

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

In an $N-P-N$ transistor amplifier,the collector current is $9 \ mA$. If $90\%$ of the electrons emitted from the emitter reach the collector,then:

The voltage gain and current gain of a transistor amplifier in common emitter configuration are respectively $150$ and $50$. If the resistance in the base circuit is $850 \Omega$, then the resistance in the collector circuit is: (in $\Omega$)

In a common base amplifier circuit,calculate the change in base current if the change in emitter current is $2\, mA$ and $\alpha = 0.98$.