Option 1 states that the reaction of heating manganese dioxide with aluminum powder is exothermic. This means that the reaction releases heat to the surroundings. In this reaction, the manganese dioxide (MnO2) and aluminum powder react to produce manganese (Mn) and aluminum oxide (Al2O3).

Option 2 states that the reaction is endothermic, which would mean that the reaction absorbs heat from the surroundings. However, this is incorrect because the correct answer states that the reaction is exothermic.

Option 3 states that manganese is produced as a solid, which is correct. In this reaction, manganese is produced in its elemental form (Mn) as a solid.

Option 4 states that manganese is more reactive than aluminum. Although aluminum is more reactive than manganese, this statement is not directly related to the reaction of heating manganese dioxide with aluminum powder. Thus, it is not the correct answer.

In summary, option 1 is correct, as it accurately states that the reaction is exothermic.