Most computer systems are (71) to two different groups of attacks：insider attacks and outsider attacks．A system that is known to be (72) to an outsider attack by preventing (73) from outside can still be vulnerable to the insider attacks accomplished by abusive usage of (74) users．Detecting such abusive usage as well as attacks by outsides not only provides information on damage assessment,but also helps to prevent future attacks．These attacks are usually (75) by tools referred to as Intrusion Detection Systems．

（73）处填（）。

A．visit

B．access

C．I/O

D．read/write

海运提单签发的日期是( )。

A．货物开始装船的日期

B．货物装船过程中任何一天

C．货物装船完毕的日期

D．签订运输合同的日期