The reaction is a synthesis…
… because <em>two substances are combining to make one other substance</em>.
It is also a <em>reduction-oxidation reaction</em> because the <em>oxidation number of Al increases</em> from 0 to +3 and the <em>oxidation number of O</em> decreases from 0 to -2.
This problem is asking for an explanation of what happens when an ionic bond is formed. Although the choices are not given in the question, one can find them on the attached file and realize the answer is C "a less electronegative atom donates an electron to a more electronegative atom" according to:
<h3>Types of bonds:</h3><h3 />In chemistry, the forces that hold atoms together are known as chemical bonds and act like connections for atoms to form compounds. There exist ionic and covalent bonds, so the formers occur when electrons are thoroughly donated from the least electronegative atom to the most electronegative one.
On the flip side, covalent bonds occur when the electrons are shared between the two or more of the atoms forming the compound. In such a way, one can discard choices A and B because they are more related to covalent bonds.
Therefore, one can select C "a less electronegative atom donates an electron to a more electronegative atom" as the correct answer, because not all the elements are able to donate more than one single electron, and the less its valency, the more ionic the compound turns out to be.
Learn more about types of bonds: brainly.com/question/792566
