What is letter A in the DNA model??

adenine (A), cytosine (C), guanine (G), and thymine (T),

Explanation:

when pollution originates on one side of a border, it often spreads through the environment beyond the point of origin, becoming a shared problem. It is important to track the sources of pollution to identify the policies and sources for prevention efforts, but regardless of the source of pollution, once a border area becomes polluted, the pollution is a health threat for all individuals on either side of the border.

Explanation:

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