A sample of Ar(g) is contained in a cylinder with a moveable piston at an initial
temperature of T. The volume of the
sample is decreased from 4.5 L to 1.5 L
while the pressure is held constant, as
shown in the diagram below.

Option (B) is correct.

Explanation:

Initial temperature of the gas is T.

The volume of the  sample is decreased from 4.5 L to 1.5 L  while the pressure is held constant.

At constant pressure, the relation between volume and temperature is given by :

Here, V₁ = 4.5 L, V₂ = 1.5 L, T₁ = T₁, T₂ = ?

So,

So, the final temperature of the gas is . Hence, the correct option is (B).