The correct answer is option a. Temperatures would rise.
The reason why the temperature of tropical ecosystem will rise because of the increased concentration of carbon dioxide is the tendency of carbon dioxide molecule to trap heat. Carbon dioxide gas is a green house gas which is capable of trapping solar energy so if more carbon dioxide will be present in the atmosphere then it will lead to the increased level of heat energy . This is the reason why the atmosphere sounds heated even in the absence of sun i.e. during the time of dusk. Carbon dioxide restricts the heat of solar energy from dissipating back into the space as a result of which the heat remains confined to the atmosphere even after the sun has disappeared.
