Answer:
A. The increase in the mass of the magnesium oxide was due to oxygen atoms in the air.
Explanation:
Burning occurs in the presence of oxygen. A chemical combination occurs between Mg and O in that the atom of magnesium attracts one another.
Mg + O₂ → MgO
Starting with the magnesium, on reacting with oxygen a new compound forms. This is why there is mass increase in the MgO compared to the starting material.
Some of the negative consequences of cobalt mining are pollution and child trafficking.
<h3>Effects of cobalt mining</h3>
Many young children are made to work in mines generally either due to continued struggle for survival or forced into it by child traffickers.
Apart from that, cobalt mining causes pollution in the environment. Inhalation of dust containing cobalt causes a host of health issues such as lung cancer and damage to human skin.
Other effects include soil degradation and pollution, water pollution due to mine run-offs, etc.
More on the effects of mining can be found here: brainly.com/question/2365629
