The man died because medical help was not summoneD. A doctor should _____.
A. be have called
B. been called
C. be called
D. have been called
Chọn đáp án D
Vitamin C _____ by the human body. It gets into blood stream quickly.
Last night a tornado swept through Rockville. It _____ everything in its path.
Today, many serious childhood diseases _____ by early immunization.