It was 80 years before Christopher Columbus crossedthe Atlantic______ Zheng sailed to East Africa

Because of the heavy snow, the researchers failed to reach their ________ on time as expected.

ker including some tourists ______ the Great Wall before, so they headed for the Forbidden City.

Christmas is a holiday usually celebrated on December 25th, _____the birth of Jesus Christ.[ ]

The old woman ______ her sons and daughters ______ and see her from time to time.