单项选择题
Economies, several courses of which I have taken thus far, （） to be difficult but useful for almost all students.
A. prove B. proves C. have been proved D. are proved
单项选择题 The bedroom is in perfect condition, （） a few scratches on the wall.
单项选择题 No sooner （） the news than they rushed out into the street.
单项选择题 Which of these trains is the one （）goes to Nanjing
