Which of the following sentences contains formal language, rather than informal language?

D does not use complete words to explain and also uses the word “ton” which is informal in nature as compared to other sentences.

The peer review process is never an easy one and takes a lot of time and attention.

likewiseis used when you are comparing two methods, states, or situations and saying that they are similar.

The plural of words ending with “f” are usually replaced with “ves” at the end, making the C the correct answer.

Although means 'in spite of something'.it is a subordinating conjunctions.This means thatthe clause which they introduce is a subordinate clause, which needs a main clause to make it complete

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.

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

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.

"We sat down to eat our meal outside; the night was beautiful." The semicolon (;) is used correctly in this choice.

Choice A has a comma before and which makes it incorrect.
Choice C has an s after the apostrophe in ladies's, hence it is incorrect.

Choice D also has a comma before and making it incorrect.
Note: And is a joining word and hence should not have commas before or after it.

Having commas that separate the additional information “which had been parked on a steep hill” is the most correct use of the punctuation because it shows that the sentence can do without that piece of information. The additional information is only used to add more details but can still be excluded and that is why it is enclosed in commas.