Which metal is protected by a layer of its own oxide?

The reading of the ammeter in the circuit shown will be: (in $A$)

Which of the following is an example of a Gram-positive bacterium?

What are $X$ and $Y$ in the following reaction?
$CF_2Cl_2 \xrightarrow{UV} X + Y$

During an adiabatic process,the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio $C_P / C_V$ for the gas is

If $n(A) = 3$,$n(B) = 6$ and $A \subseteq B$,then the number of elements in $A \cup B$ is: