在短文空白处填写适当的词（每空不多余3个词）或所给词的正确形式。
Six men have been trapped in a mine for seventeen hours. If they are not brought to the surface soon they may lose their      (life). However, rescue operations are       (prove) difficult. If explosives are used, vibrations will cause the roof of the mine      (collapse). Rescue workers are therefore drilling a hole on the north side of the mine. They intend to bring the men up in        special capsule.       there had not been a hard layer of rock beneath the soil, they would have completed the job in a few hours. As it is, they have been drilling for sixteen hours and they still have a long way to go. Meanwhile, a microphone, which     (low) into the mine two hours ago, has enabled the men to keep in touch with the closest relatives. Though they are running out of food        drink, the men are         (cheer) and confident that they will get out soon. They have been told that rescue operations are progressing     (smooth). If they knew how difficult it was to drill        the hard rock, they would lose heart.