Final answer:
The correct punctuation mark to follow a salutation in a business letter is a colon (:), aligning with standard business letter format and etiquette.
Step-by-step explanation:
The correct answer is option a) Colon. When writing a business letter, the salutation should be followed by a colon (:), not a comma, semicolon, or exclamation point. This convention signals the start of a formal communication. For example, if you are addressing Dr. John Doe in a business letter, the salutation would read "Dear Dr. Doe:" followed by a blank line before proceeding with the body of the letter. Although less formal communications might use a comma after the salutation, the colon is traditionally used in business letters and aligns with standard business etiquette.
When writing a business letter, the salutation should be followed by a comma. For example, if your salutation is "Dear Mr. Smith", you would write it as "Dear Mr. Smith," with a comma after the name. This is the standard punctuation rule for business letters.