B. T1 is three times smaller than T2
The temperature change due to reaction is only possible through the reaction. The first set of concentrations are stoichiometric – equal amounts will react completely, generating a temperature change related to the overall moles of compounds involved in the reaction.
In the second case the molarity is increased by three. With three times the number of moles available to react, and with stoichiometric quantities available, the net change in solution temperature will be three times the original reaction temperature rise, or T1 is three times less than T2.