Without facts,we can’t form a worthwhile opinion for we need to have factual knowledge       

our thinking. [ ]

A.which to be based on

B.which to based on

C.on which to base

D.to which to be based

在加氢装置试压气密时，一般微漏，可不降压，直接上紧法兰，实际工作中往往需要使用液压扳手进行螺栓紧固，液压扳手紧固时（）。

A、一直紧到紧不动为止

B、根据液压扳手规定的使用力矩上限确定螺栓的最高紧固力矩

C、应注意上紧力矩不能超过螺栓设计规定值

D、无严格要求，随便紧