If a rock sample has a half life of 10 years, and has 100 atoms of parent material today, how many half lives will have passed before it has only 25 atoms of parent material left?

1 half life,2 half life's to equals 25 atoms left.The 1 half life gets the amount of atoms to 50.Two half life's gets the amount of atoms to 25.Half life's takes the amount of substance and Half's it every certain amount of years.

The correct answer is B) Heavy metals such as mercury.

Explanation:

Heavy metals such as mercury or lead are denser than regular metals, this causes it is common for these metals to be found in the surface of Earth rather than in the air or atmosphere. Indeed, mercury and other similar metals are extracted from the Earth's crust and then used for different purposes. As a result of this, mercury ends up in the surface of Earth or in water sources which causes soil or water pollution. This means mercury is not a common source of air pollution; on the opposite other such as CFCs, nitrogen oxides and smog remain in the air and therefore are sources of air pollution.