Answer:
In a chemical change, the atoms in the reactants rearrange themselves and bond together differently to form one or more new products with different characteristics than the reactants. When a new substance is formed, the change is called a chemical change.
Explanation:

. Iron is divalent to hydrogen and water.
When humans burn fuel/cut down tress, they will increase the level of carbon dioxide within the atmosphere. Tress "inhale" the carbon dioxide within the atmosphere and without them, the excess will still linger. Carbon dioxide is a byproduct of burning fuel thus, it will increase the levels in the atmosphere.
It's B - convection that is correct...