It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it.
He was very busy yesterday, otherwise he ____ to the meeting.
Sometimes our opinions differ _________ what we choose to observe and how we deal with what we’ve observed
– Will you please go to see the movie Guanyinshan with me? – No, I won’t. I it already. A. saw B. have seen C. see
________ people were hurt in the accident.
Gun control is a subject ______ Americans have argued for a long time.