is kept

• He is in a coma and is being kept alive by a life-support machine .
  他处于昏迷，靠生命维持器活着。
• The police have been keeping a close watch on the suspects' movements .
  警方一直严密监视着可疑分子的活动。
• The defense department doubted that the attacks could be kept secret .
  国防部怀疑能不能对这些袭击保守秘密。
• The patient is seriously ill and is being kept under continuous observation .
  病人病情严重，现接受持续观察。
• In actual operation, the fuel is kept at an almost constant level .
  在实际运行中，燃料几乎保持在一定的水平上。
• Most of the excess cars were kept on huge lots in the detroit area .
  大部分积压的车子都成堆地存放在底特律地区。
• As business went beyond the barter stage, records had to be kept .
  当商业超越了以物易物阶段之后，就需要保存某些资料。
• They clearly could not be kept on board these tiny ships indefinitely .
  他们显然不能无限期地被关闭在狭窄拥挤的舰艇上。
• Film should be kept clean, dust free, and handled only by the edges .
  胶片应保持清洁，没有灰尘，用手只能拿胶片的边部。
• The u-boat packs were kept underwater and harried continually .
  成群结队的德国潜艇被迫潜伏在海底，并且不断地受到困扰。