A closed 2.0 L container initially holds 3.0 mol of $$\text{O}_2$$ (g) and 2.0 mol of $$\text{N}_2$$ (g) at room temperature, T. If the pressure remains constant when 1.0 mol of $$\text{O}_2$$ (g) is added, the final temperature of the system is (assume ideal gas behaviour throughout)

A

$$\frac{3}{5}T$$

B

$$\frac{5}{6}T$$

C

$$2T$$

D

$$\frac{6}{5}T$$