Answer:
A. not wearing goggles when breaking a rock with a hammer
Explanation:
You could get extremely hurt if you are not wearing goggles while doing lab work.
In order to balance an equation, we apply the principle of conservation of mass, which states that mass can neither be created nor destroyed. Therefore, the mass of an element before and after a reaction remains constant. Here, the balanced equation becomes:
4Al + 3O₂ → 2Al₂O₃
The coefficients are 4, 3 and 2.