86. If there is no one to help him with the preparation，he will have to put off the meeting
87. As soon as she tears open the letter，Mrs. White will find out what has happened to her Husband
88. Unless the government agrees to give extra money，the theatre will have to be closed next month.
89. You couldn't have seen Jane in her office last Friday，for she's been out of town for two weeks.
90. Scientists have searched for many years for a method to tell whether a volcano explosion will be small or large.
81. I always regret not studying harder when I was young.
82. Her dog ran out of the yard as soon as the old lady opened the gate.
83.Not until he finished his homework did his mother allow him to watch TV in the evening.
84. The boys spent the whole morning discussing possible answers to the question
85. It's reported that by the end of last month the sale of the company had risen by 10%.