Which of the following sentences is grammatically incorrect?

Question

Quizplus · Accepted Answer

"Sylvia became a vegetarian last year her husband still eats meat" is grammatically incorrect because it is a run-on sentence.
Run-on sentences are when two or more complete sentences are written as one sentence. Run-on sentences can be fixed by adding a dash (-), a semicolon (;), or a colon (:) between the two sentences. You could also add a coordinating conjunction with a comma (, but) or make them two separate sentences with a period (.).
Any of these would be considered correct:
Sylvia became a vegetarian last year - her husband still eats meat.
Sylvia became a vegetarian last year; her husband still eats meat.
Sylvia became a vegetarian last year: her husband still eats meat.
Sylvia became a vegetarian last year, but her husband still eats meat.
Sylvia became a vegetarian last year. Her husband still eats meat.

Which of the Following Sentences Is Grammatically Incorrect