Which of the following is correct, about doping in a transistor ?

For transistor action 

(1) Base, emitter, and collector regions should have similar size and doping concentration

(2) Base regions 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 and the base-collection junction is forward biased

Which of the following pairs of statements is correct?

In a common emitter transistor amplifier, the output resistance is $500 \mathrm{K}\Omega$ and the current gain $\beta =49.$ If the power gain of the amplifier is $5\times {10}^6,$ the input resistance is

A transistor oscillator is

(i) an amplifier with positive feedback

(ii) an amplifier with reduced gain

(iii) the one in which dc supply energy is converted into ac output energy. Then