When the transistor is used as an amplifier,

The phase difference between the input voltage and the output voltage in a common emitter amplifier is (in $^{\circ}$)

For transistor action:
$(1)$ Base,emitter and collector regions should have similar size and doping concentrations.
$(2)$ The base region must be very thin and lightly doped.
$(3)$ The emitter-base junction is forward biased and base-collector junction is reverse biased.
$(4)$ Both the emitter-base junction as well as the base-collector junction are forward biased.
Which one of the following pairs of statements is correct?

For a transistor,$\beta = 100$. The value of $\alpha$ is

In an experiment,the input characteristics are shown for a $CE$ configuration $n-p-n$ transistor for different output voltages. Based on the graph,which of the following is correct?

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: