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PUNCTUATION, MULTIPLE

When two or more marks of punctuation are called for at the same place in the sentence (not counting parentheses, brackets, dashes, and quotation marks), only the strongest is retained.

From strongest to weakest:
            exclamation point, question mark, period, dash, colon, semicolon, comma.

The period in an abbreviation is retained before all marks of punctuation except for the period ending the sentence:
            Homo sp.?, DuPont Co.

Retain a question mark or exclamation point at the end of a title and use other punctuation as required, even if it results in multiple punctuation—except at the end of a sentence when the final period should be omitted:
            Recorded in EXPLORER's film Landslide!, the collapse that had been predicted for years finally happened.
            I really enjoyed the film Landslide!