David entered the class. Beside his desk ______ he had never seen before.

(单选题)You cannot go outside since it is too late; _____ it is rain (单选题)It will be many years ______ the doctors and medical scienti (单选题)______ to the polluted air is dangerous for our health. (单选题)At present, there are many instances ______ the governments (单选题)The auto-company succeeded in developing a new type of new e (单选题)—What do you think of her suggestion?—______, it would be mu (单选题)My brother left home five years ago. I ______ nothing from h (单选题)He regretted ______ a second-hand car. (单选题)Please put these teaching materials in order and don’t leave (单选题)—What does the sign over there say?—No person ______ enter t