单项选择题
One of the serious problems facing us is（）of how to get enough manpower,
A. that B. it C. which D. what
单项选择题 There has been a decrease（）the number of students entering the Medical College this year.
单项选择题 Are you going to keep me（）all day long
单项选择题 （）ballpoint pen was invented by（）Hungarian refugee named Lazlo Biro.
