According to the lastest study ,the population of Xuzhou has grown to more than 30 times____it was in 1949. The figure ____to 9.5 million by the end of 2010.
—Can we ski on this mountain? —Of course.However, at no time _______ you do so alone.
He _______ have completed his work;otherwise, he wouldn’t be enjoying himself by the seaside.
He must have been late for the conference yesterday, _______?
He _______ more visits to his parents.He has been regretting not doing so since they passed away.
Some aspects of a pilot’s job _______ be boring,and pilots often _______ work at inconvenient hours.