Although he was in poor health, Robert succeeded ______ other more famous engineers failed.
Mathematics _______ the language of science.
Stories of the Long March _______ popular with the young people now.
Three million tons of coal ______ every year in the city.
There _____ a lot of rubbish on the floor so I asked Mary to sweep _____ up.
The Olympic Games in the year 2008 ______ in Beijing of China, which ______ known to us all.