单句改错 ( 每句仅 1 处错误 ) 1 . There is no doubt whether global warming is a security threat to us all. 2 . They have retrained the number of young technicians for our factory. 3 . Much damage has done to the car; you'd better get it repaired. 4 . Though I told him over and over again to be careful when driven , he wouldn't listen. 5 . Whether he could get the support from his parents made great difference to the plan. 6 . She was watching TV while the doorbell rang.