Decide which element probably has a boiling point most and least similar to the boiling point of aluminum. Comparing boiling point:
gallium rubidium magnesium oxygen
most similar to aluminum
least similar to aluminum

The boiling point of gallium would be most similar to aluminum, and the boiling point of oxygen would be least similar to aluminum.

Explanation:

The atomic number of aluminum is 13, in the periodic table, magnesium lies in a similar period as Aluminum and Gallium is also present in a similar group. Thus, it can be expected that both magnesium and gallium exhibits similar boiling points with aluminum. However, gallium is a poor non-metal just like aluminum, while magnesium is a metal. Thus, it can be said that the boiling point of aluminum is more similar to gallium.

Now of the given elements, oxygen is a gas, thus, the boiling point of oxygen would be least similar to aluminum.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.