Which version correctly punctuates the nonrestrictive clause in the sentence about 30 Rock?

• A. The characters and plot lines of 30 Rock as most of the show's fans know grew out of Tina Fey's experiences at Saturday Night Live.
• B. The characters and plot lines of 30 Rock, as most of the show's fans know grew out of Tina Fey's experiences at Saturday Night Live.
• C. The characters and plot lines of 30 Rock, as most of the show's fans know, grew out of Tina Fey's experiences at Saturday Night Live.
• D. The characters and plot lines of 30 Rock as most of the show's fans know, grew out of Tina Fey's experiences at Saturday Night Live.

Answer: (C)

Nonrestrictive clauses add extra information and should be set off with commas. In this sentence, the phrase as most of the show's fans know provides additional information about what most fans know and does not limit which characters and plot lines are being discussed. Because it’s nonessential, it should be enclosed by commas. The best version places a comma before the as-clause and another comma after it: The characters and plot lines of 30 Rock, as most of the show's fans know, grew out of Tina Fey's experiences at Saturday Night Live. The other options fail because they omit one of the required commas or misplace the punctuation, making the as-clause either feel essential or awkward to read.