In an $NPN$ transistor,the collector current is $20 \, mA$. If $90\%$ of the electrons emitted reach the collector,then:

Given below are two statements:
Statement $I :$ $PN$ junction diodes can be used to function as a transistor,simply by connecting two diodes back-to-back,which acts as the base terminal.
Statement $II :$ In the study of transistors,the amplification factor $\beta$ indicates the ratio of the collector current to the base current.
In the light of the above statements,choose the correct answer from the options given below:

In an $npn$ transistor, $10^{10}$ electrons enter the emitter in $10^{-6} \; s$. If $4\%$ of the electrons are lost in the base, the current transfer ratio $(\alpha)$ will be:

In the case of constants $\alpha$ and $\beta$ of a transistor:

An $npn$ transistor operates as a common emitter amplifier,with a power gain of $60\, dB$. The input circuit resistance is $100\,\Omega$ and the output load resistance is $10\, k\Omega$. The common emitter current gain $\beta$ is:

An oscillator is nothing but an amplifier with