Which of the following figures correctly shows the phase relation between the input signal and the output signal of a common-emitter transistor amplifier?

Given below are two statements:
Statement $I$: Photovoltaic devices can convert optical radiation into electricity.
Statement $II$: Zener diode is designed to operate under reverse bias in the breakdown region.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following $p-n$ junction devices is not used in reverse bias?

$A$ thermoelectric refrigerator works on

The box in the circuit below has two inputs marked $V_{+}$ and $V_{-}$ and a single output marked $V_{o}$. The output obeys the following relation:
$V_{o} = \begin{cases} +10 \, V & \text{if } V_{+} > V_{-} \\ -10 \, V & \text{if } V_{+} < V_{-} \end{cases}$
Which of the following graphs represents the output $V_{o}$ as a function of time $t$?

In which of the following circuits is the junction reverse biased?