Which of the following sentences is the most formal in style?

The subject is in plural “tennis balls” and is supported by a plural verb “roll” which makes D the correct use of subject-verb agreement.

A capital letter is usedfor the first word of a sentence and for all proper nouns (words that name a specific person, place, organization, or thing). Capitalization in D is used to indicate the organization and compared to other others that do not follow the requirements for using capital letters, it makes D the correct answer.

The word crisis has a plural of “es” making B the right answer.

A complete sentence has a subject (noun), verb, capital letters, punctuation and finally must make sense. B is the only complete sentence that explains the action and nouns in a way that makes sense.

Signing in this sentence describes a noun as it is a “thing” rather than an action.

"Don't stay out too late," My mother said - is incorrect. The "m" should be lowercase, not capitalized.

"I have to leave!" she said - is correct. This sentence is correctly punctuated. The exclamation mark is placed inside the quotation marks to indicate that she is speaking with excitement.

"Were you late to the show," he asked - is incorrect. The question mark should be placed inside the quotation marks when it is part of the quoted speech. The correct punctuation would be: "Were you late to the show?" he asked.

"It's time to go home." I told him - is incorrect. A comma should be placed inside the quotation marks instead of the period.

Using previous submitted work is plagiarism on itself even when that work belong to the student in question.

The word “wow” can certainly be marked as an interjection as the word is in useto show the emotion of “surprise” of the speaker about the ability of the addressed person to qualify the hurdle in the first attempt.

Therefore is used to affirm the first part of the sentence into showing why the second one should be mentioned.

A citation is normally used to cite specific information that has been researched by other people. D is only showing a location and not necessarily a product of a research and hence does not need any citation.