Introductory or interrupting phrases (i.e. phrases that are subordinate and add information to a sentence, but are not necessary to the sentence being complete) must be separated from the rest of the sentence by commas. In the provided sentence, "The great teacher exhausted" should read "The great teacher, exhausted."

An introductory phrase must always be separated from the rest of the sentence by comma. Introductory phrases are phrases that provide information about, or modify, the subject of the main clause, but are not essential to the grammatical structure of the sentence. In this sentence, the phrase "Although the students had studied hard" acts as the introductory phrase, so it must be followed by a comma. This makes the correct answer "hard they found."

The phrase "even though he had been so good" is a non-essential interrupting phrase. The sentence would still be correct even if it were deleted. Therefore, there must be commas before and after the phrase, which means that the the correct answer is "so good his mother."

In the sentence above, the phrase "the former vice president" is an appositive phrase that renames Corrine. Because commas are required before and after an appositive phrase, "the former vice president" must have commas before it and after it. This means that the correct answer is "Corrine the former."

In this sentence, the phrase "As luck would have it" is an introductory phrase. Because an introductory phrase must be followed by a comma, the sentence should read "As luck would have it, there were no open appointments on Kendra's only day off from work." This makes the correct selection "have it there."

An introductory phrase must always be followed by a comma. In this sentence, the phrase "Just as the students had feared" acts as an introductory phrase, so it must be followed by a comma.

In the example sentence "If you're going to be staying here long" is clearly a dependent clause (big clue being the "if") because this clause provides context and precedes the main clause, it is called an introductory clause. The only correct way to punctuate an introductory clause is to add a comma after the last word in the phrase, which in this case is "long."

Interrupting phrases are subordinate and add information to a sentence, but are not necessary to the sentence being grammatically complete. Such phrases must be separated from the rest of the sentence by commas at the beginning and end of the phrase. In the example sentence "one of the smartest young women I have ever met" acts as an interrupting phrase, so the portion of the sentence above that needs to be corrected is, "met can't."

In the example sentence "commonly known as the Poison King" is a grammatically unnecessary (but contextually useful) phrase that must be separated from the clause it interrupts with commas. The sentence above is missing a comma between "Mithridates" and "commonly." The rest of the sentence is grammatically correct and complete.

The fundamental grammatical structure of the example sentence reads, "Pontus is famous for its extraordinary plant life." "Pontus" is the subject, while "is" functions as the verb. So, we know that the words excluded from this fundamental subject-verb-object structure must be an interrupting phrase, and as such must be separated with commas at the beginning and end of the phrase. The example sentence is missing a comma after "Sea."