--- What’s three and four?--- ______.
—More and more students wear glasses now. —______.
—Jim, do you know the reason _____ Bob kept silent during the discussion? —I guess he was thinking about his sick dog. It might be dying.
We’ll leave for senior high schools soon. It’s really difficult _______ goodbye to our teachers and friends.
—Let’s climb the mountain. —I don’t agree. _______ the mountain will make us exhausted.
—What ______ in your school in the past few years? —A new library and a playground were built last year.