(a) Exothermic. Combustion reaction releases heat

(b) Endothermic. Water in liquid state absorbs energy to break the hydrogen bonds between the water molecules to form water in gaseous state

(c) Endothermic. Heat is absorbed to break the hydrogen bonds between the water molecules in solid state to form liquid state water.

The reactants must have a much higher bond strength than its product so that the reaction will release a large amount of energy to cause a good explosion.

Heat is the total energy possessed by the molecules in a piece of matter while Temperature is the average kinetic energy of a single particle in a system per unit of space.

Take for example,
A small bottle of drinking water might have the same temperature as a large pot of water, but the pot of water has more heat compared to the small bottle of drinking water as the large pot of water has more water and hence more total thermal energy.

(a) It tells me that since gasoline has an octane rating of 98, it is very prone to knocking hence it will have higher efficiency to ignite the fuel.

(b) It tells me that the fuel contains quite a high amount of oxygenates.