完成句子（共10小题，每小题1.5分，满分15分）
阅读下列各小题，根据括号内的汉语提示，用句末括号内的英语单词完成句子，并将答案写在答题卡上的相应题号后。
71. ______________ (席地而坐) are a group of young people who come from all over the world, exchanging ideas about their own cultures. (seat)
72. The whole world is amazed at _________________ (中国取得的巨大进步) since the policy of the reform and opening up was carried out. (progress)
73. ______________ (暴露在强烈的阳光下) too long will do harm to your skin. (expose)
74. When he came back to himself, he ________________（发现自己被锁）in a damp basement. (lock)
75. I don’t quite understand  _________________ (是为什么) several murders of kindergarten children happened in China recently. (why)
76. Nowadays_______________ (值得一看的东西) in the museum has attracted a lot of visitors all over the country. (worth)
77. If you had come here 10 minutes earlier, you would have heard _____________ (在讨论什么). (discuss)
78. He may not come today, ___________ (如果是那样的话) there is no need to wait any longer. (case)
79. All flights _______________ (被取消了) because of the terrible weather, they had to go there by train. (cancel)
80. Do you feel like dining out for a change or would you rather we two _______________ (吃晚饭) at home? (have)