What is the most serious effect of water pollution created by human activity?

It can affect the health of people or animals.  

Explanation:  

Contaminated water can pose a serious risk for both animals and humans. Animals and plants that live in this water often die because of this pollution. Even if a certain animal does not die because of the contamination, it would likely die because of the changes in the food chain. Animals and people that drink their water from this source can become sick from the bacteria and the diseases that are often carried in this water.

It can affect the health of people or animals. It can affect the air surrounding it. It also can interfere with future building in the area.

Explanation:

the answer to the question is a

the statement that best explains why the tenth amendment reserves some rights and powers to states is that the framers believed in the principle of federalism. this principle says that some powers are in the hands of a centralized national government, while others are reserved for the governments of several states.