Air pollution is best defined as a. gases or particles present in high enough concentrations in the atmosphere to harm humans, other organisms and structures b. suspended particles of gases that contain small amounts of solids and liquids c. organic chemicals that can vaporize into the air d. any gases in earth's atmosphere in trace amounts e. small particles in the atmosphere arising from volatile organic compounds

Answer;

A. gases or particles present in high enough concentrations in the atmosphere to harm humans, other organisms and structures.

Explanation;

Air pollution is a type of pollution that occurs when harmful or excessive substances such as particulates, gases and biological molecules are introduced into Earth's atmosphere.

The burning of fossil fuels, such as coal, oil, natural gas, and gasoline to produce electricity and power our vehicles is the major cause of air pollution.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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the sphincter muscles at the end of the digestive tract is the anus.