What is one reason chlorination would be preferred over ultraviolet radiation?
a) chlorine only eliminates visible impurities and is ineffective against microorganisms.
b) chlorine not only kills bacteria but provides a residual effect on returning microorganisms.
c) uv radiation can be used only to treat drinking water and is ineffective in treating waste water.
d) ultraviolet radiation is more effective because it reduces the ph of water and destroys all bacteria.

The correct answer is option- B.

Explanation:

Chlorine is a granular powder or liquid are used to treat water or the contaminated liquid to remove or kill the bacteria or microbes. UV lights are also used to remove the microbes but the residual effect persists long.

The chlorine does not just kill the microbes but also provide a residual effect on returning microbes.

Thus, the correct answer is option- B.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

blah

explanation:

bc blah