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."

Introductory phrases are subordinate and add information to a sentence. These phrases are not necessary to the sentence being grammatically complete, and thus must be separated from the rest of the sentence by commas. In this sentence "Every morning when Kent comes to school" acts an introductory clause, and must be punctuated with a coma after "school." The portion of the sentence above that needs to be corrected is, "school he"

In the example sentence, "if you don't stop smoking" is clearly a dependent clause. Since this dependent clause comes before the main clause, it is acting here as an introductory phrase and must be punctuated with a comma.

Interrupting phrases must be separated from the rest of the sentence with commas. Here, the grammatical subject is "pork," this subject is then described in a grammatically irrelevant, but contextually useful, interrupting phrase. Because it is outside of the basic structure of the sentence, the interrupting phrase "one of my favorite kinds of meat" should have one comma at the beginning and one comma at the end.

In this sentence "Derek Jacobi" acts as an interrupting appositive phrase, and thus must be enclosed with commas. Here, the subject is first identified as "my favorite actor of the previous generation," and is then renamed with a proper noun. The actors name is important information contextually, but is not fundamental to grammatical structure of the sentence, since the grammatical subject remains "my favorite actor of the previous generation."

The underlined portion of the sentence contains just one error. The word "Shortly" is used as an introductory phrase, describing when the action of the sentence took place. Any introductory phrase needs to be set off by a comma. "Shortly, the windows opened" is the best choice to improve the sentence.

Commas, gramatically speaking, should never be used before or after the word "that." The correct sentence would have: "James finally saw the movie that his friends . . ."

"Had recommended" could be changed to "recommended", for the sake of simplicity, but the comma error is more flagrant.

The sentence consists of two independent clauses ("Joey will reluctantly eat broccoli and spinach" and "his favorite green vegetables are peas and green beans") joined by a coordinating conjunction, "but." (Other coordinating conjunctions can include "and," "or," "nor," "yet," "so," and "for.") When two independent clauses are joined by a coordinating conjunction, a comma is required after the first clause immediately before the conjunction. The corrected sentence would read, "Joey will reluctantly eat broccoli and spinach, but his favorite green vegetables are peas and green beans."