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【单选题】
常态下阀门的阀口常闭,出油口接油箱,当系统压力低于阀门的调定压力时,阀门不工作。当外负载增大,系统压力升高到阀门的调定压力时,阀打开,系统压力不再升高,将始终稳定在阀门的调定压力值。该文字叙述的阀门为?A.
顺序阀
B.
单向阀
C.
减压阀
D.
溢流阀
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举一反三
【单选题】He was so committed to the ______ of his faith that he was unable to evaluate them impartially.
A.
credits
B.
doctrines
C.
certificates
D.
documents
【单选题】The term paper was due to December 1, but hard as he tried, he was unable to meet the _____ for it.
A.
challenge
B.
need
C.
deadline
D.
date
【单选题】He was unable to make much progress, hard ______ he tried.
A.
unless
B.
as
C.
however
D.
because
【简答题】左连接查询(LEFT JOIN 或 LEFT OUTER JOIN) (1)为文章表添加一条记录 (2)利用左外连接对文章表和栏目表进行查询
【简答题】He is unable to answer the questions about the new text．He__________it yesterday．
【单选题】左外连接查询中，主表在（ ）
A.
LEFT OUTER JOIN的左边
B.
LEFT OUTER JOIN的右边
C.
RIGHT OUTER JOIN的左边
D.
RIGHT OUTER JOIN的左边
【单选题】He was unable to make such progress, __________________.
A.
as he tried hard
B.
as hard he tried
C.
so hard did he try
D.
hard as he tried
【简答题】INNER JOIN代表___连接;LEFT OUTER JION代表___连接。
【单选题】Why is the woman unable to contact a colleague?
A.
He is at the office on Falcon Street.
B.
He is out of town.
C.
He has switched off his cell phone.
D.
He is in a discussion.
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