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【单选题】
根据机械效率,判别机械自锁的条件是( )。A.
η≥1
B.
η≥0
C.
η≤0
D.
η≤1
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反馈参考答案：
举一反三
【单选题】She found her book this morning,but now she her pen.
A.
loses
B.
is missing
C.
has lost
【单选题】She is ______ there and ______ a book now. [ ]
A.
siting; seeing
B.
sitting; looking
C.
siting; reading
D.
sitting; reading
【单选题】—What is Lucy doing now? —She _____ a book.
A.
read
B.
reads
C.
reading
D.
is reading
【简答题】国家建立统一领导、（）为主的应急管理体制。
【单选题】—What does your sister usually do in the evening? —She usually______ TV, but now she _____ a book. .
A.
watch; read
B.
watches; is reading
C.
is watching; sees
D.
watches; is seeing
【单选题】-What is she doing now? - She _____ a book.
A.
reads
B.
read
C.
is reading
D.
has read
【单选题】Did she buy that book just now?的正确陈述句是____
A.
She buys that book just now.
B.
She buyed that book just now.
C.
She buy that book just now.
D.
She bought that book just now.
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