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. The situation of unemployment has not been so serious ___________________________ (所期待的).  (expect)
72. Tom has been playing basketball on the playground, ___________________________ (脸上全是汗水).  (cover)
73. ___________________________ (余下要做的) is an accurate description of the long process of the experiment.  (leave)
74. It’s widely accepted that never in history ___________________________ (有过) a more successful opening ceremony than that of the Beijing Olympics.  (there)
75. During my last trip my cellphone was left in a hotel accidentally, ______________________  (再也找不到) .  (find)
76. He told us that he was very happy ___________________________ (他现在的处境) . (be)
77. Qian Xuesen went to California from 1935 to 1955, ___________________________ (在那时期) he concentrated on the research into jet planes.  (period)
78. I have no idea whether the machine can be used again but it __________________________ (在维修) in the morning.  (repair)
79. Did you know ___________________________ (到底怎么) the nuclear explosion occurred in Japan?  (it)
80. The air hostess required that___________________________ (我们坐着) until the plane had come to a complete stop.  (remain)