Question #N910

The word "then" can be used as an adverb, as in "She ran to the window, then looked out." It can also be used to introduce a clause, as in "She ran to the window, then she looked out." Both uses are correct, but they serve different functions. In the second sentence, the word "then" can be removed without changing the meaning, but the sentence in the first example would be grammatically incorrect if the word "then" were removed. Which sentence correctly uses the word "then" as an adverb?

Which of the following sentences correctly uses the word "then" as an adverb?
A. He took a moment to collect his thoughts, then he turned and walked out of the room.
B. He took a moment to collect his thoughts, then he turned and walked out of the room.
C. He took a moment to collect his thoughts, then turned and walked out of the room.
D. He took a moment to collect his thoughts, then walking out of the room.