What do all types of nuclear reactions have in common, and how do they differ from each other
a. all processes change total mass number and total charge
b. all processes conserve total mass number and total charge.

Explanation:

Nuclear reactions are defined as the reactions in which there occurs change in the nucleus of an atom. As neither electrons or protons are not involved in a nuclear reaction.

For example,

According to law of conservation of mass, mass can neither be created nor it can be destroyed but it can be converted into one form to another.

Hence, in nuclear reactions mass remains conserved.

Also, there is no involvement of electrons and protons. So, there occurs no change in charge of the atoms. Therefore, charge also remains conserved in a nuclear reaction.

Thus, we can conclude that all types of nuclear reactions have in common that all processes conserve total mass number and total charge. Whereas they differ in specific particle consumed and produced.

your picture is not part of the scientific method.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.