______is estimated that a round-trip to Mars would take more than a year.A,That B,what C,There D,It
To be able to catch up with the other students, he needs ___ hard work; he needs your encouragement, too.
___ you have finished your homework, you can go and play with your friends.
She knows so much about England. She ___ there before.
She __ the table and said the dinner was ready.
Students learning ability shouldn’t be ___ only by examination results.