A. It's a beautiful day.
B. Its a beautiful day.
C. Its' a beautiful day.
D. It a beautiful day.
Answer: It's a beautiful day.
A. It's a beautiful day.
B. Its a beautiful day.
C. Its' a beautiful day.
D. It a beautiful day.
Answer: It's a beautiful day.
Additional Information: An apostrophe indicates omitted letters or possession.
Subjects: Punctuation, Grammar