Answer:
D. Flooding occurs when too much rain falls upstream.
Explanation:
Flooding is not a change in a watershed.
A, B, and C are wrong. They all represent changes in a watershed.
Well on the periodic table Cl is in the section saying it is a non metal. In addition, it is nonmetls because it is usually a gas while metals are not. Finally, it is a non metal because it usually gains electrons instead of losing them during a reaction unlike metals.