D because 0 is always ignorant in significant figures. hope that helps:)
Answer:
6 moles of oxygen are needed to make 12 moles of magnesium oxide.
Explanation:
First of all you should know that the balanced chemical equation is:
2 Mg + O₂ → 2 MgO
The rule of three or is a way of solving problems of proportionality between three known values and an unknown value, establishing a relationship of proportionality between all of them. That is, what is intended with it is to find the fourth term of a proportion knowing the other three. Remember that proportionality is a constant relationship or ratio between different magnitudes.
If the relationship between the magnitudes is direct, that is, when one magnitude increases, so does the other (or when one magnitude decreases, so does the other) , the direct rule of three must be applied. To solve a direct rule of three, the following formula must be followed:
a ⇒ b
c ⇒ x
So:

In this case the rule of three applies as follows: if 2 moles of magnesium oxide are produced from 1 mole of oxygen, 12 moles of magnesium oxide from how many moles of oxygen is produced?

moles of oxygen= 6
<u><em>6 moles of oxygen are needed to make 12 moles of magnesium oxide.</em></u>
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Electron
Atoms, compounds, and molecules undergo chemical reactions to form new substances. In general, reactions proceed to produce products which are have more stability.
These chemical reactions are possible because of the ability of substances to form chemical bonds with other substances. These formation of bonds are primarily attributed to electronic interactions (i.e. the valence or outer electrons of the atoms). of substances.
Atoms are able to form new substances by gaining, losing, or sharing electrons with other atoms.
A chemical separation is a separation method that involves change in the chemical composition of one of the solutions that are to be separated in order to a new physical properties of one part reached leaving the rest alone.
For example, When we add a chemical to the solution that will precipitate only one part of the solution leaving the rest.
A physical separation is a separation in which solutions are separated on the basis of their physical properties.
For example, If we use physical separation method in separating two oils with different specific volumes then these two oils are separated on the basis of their settling.