Most of the students enjoy_____ stamps.
54. It's very cold outside. You should put on more clothing to ______, otherwise you will catch bad cold.
53. I’m afraid I can’t keep _______ my classmates as I’ve missed so many lessons. I have to ask my teacher for help.
52. _____ I went to the hospital to see Jack, who had _____ had an operation.
51. They planned to go to Beijing for sightseeing, but because of their daughter’s unexpected illness they had to stay at home _____.
50. The lazy boy got up very late and went to school in a hurry. When he arrived at school, he found that he had put his socks on _______.