Final answer:
The sentence that is punctuated correctly is: It is time to register for classes?
Step-by-step explanation:
The sentence that is punctuated correctly is: It is time to register for classes?
It is the only sentence that ends with a question mark and does not have any unnecessary punctuation or capitalization?
Incorrectly punctuated options: OIt is time to register, for classes? and Is it time to register? for classes?
Learn more about Punctuation in English sentences