The cyanide is

A carbon atom has 4 valance electrons and nitrogen has 5. Below is a Lewis-dot-structure of cyanide.
:N≡C.
The carbon atom is still one electron short of having a full octet and so it will seize another electron from almost anything, making the cyanide ion negative and whatever it took the electron from it now positive.
Answer:
A. Dark-colored moths become common after tree trunks become
dark.
Explanation:
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