Suppose You Had Two Atomic Gases That React to Form $\rarr$

Suppose you had two atomic gases that react to form a diatomic gas A + B $\rarr$ AB.Suppose you perform this reaction with 1 mole each of A and B in a thermally isolated chamber so no heat is exchanged with the environment.The temperature of the final system

A) will remain the same.
B) will decrease.
C) will increase.
D) could either increase or decrease depending on information that has not been provided in this problem.