Well,
Let's start with these rules:
1. There should be a comma before a(n) direct/indirect quotation.
2. The ending punctuation should be before the close quotation.
3. The quotation should begin with a capital letter.
Option A does not have a comma, and does not capitalize the first letter, so it is eliminated.
Option C does not have a comma either.
Option B's exclamation mark is outside of the quotation marks, which excludes that.
The only option left is D, which is the correct answer.
