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【单选题】
已知两个正弦量为 , ,则( )A.
u1比u2超前30度
B.
u1比u2滞后30度
C.
u1比u2超前90度
D.
不能判断相位差
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举一反三
【单选题】Ten years ago ___ only one building in our school. And in 10 years, ___ five buildings in our school. [ ]
A.
there will be, there are
B.
there was, there are
C.
there was, there will be
D.
there will be, there was
【简答题】按总线各元器件的总体总部局结构划分,主板可分为AT主板和____主板。
【单选题】Our teacher ____ in our school for 29 years and he ____ here when he was 23 years old.
A.
has taught has come
B.
taught , comes
C.
taught , came
D.
has taught, came
【单选题】Our math teacher ______ in our school for 20 years and he ______ here when he was 23 years old. [ ]
A.
has taught, has come
B.
taught, comes
C.
taught, came
D.
has taught, came
【单选题】No one knows what _______ in fifty years.
A.
will our life be like
B.
is our life like
C.
our life will be like
D.
our life is like
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