help me which one is the right answer?

Answer:
The correct option is (b).
Explanation:
The ideal gas law is given by :
[tex]PV=nRT[/tex]
Where
P, V and T are pressure, volume and temperature of the gas
R is gas constant
[tex]V=\dfrac{nRT}{P}[/tex]
If n,R and P are constant,
[tex]V\propto T[/tex]
i.e.
At constant pressure, the volume of a gas is directly proportional to its temperature. Hence, the correct option is (b).