单项选择题

感应电动机的调速途径不包括()。

A、改变定子极数
B、改变定子频率
C、改变定子电阻
D、改变转差率

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典型的软件再工程分为()类活动

A.4
B.5
C.6
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She was so angry at all he was doing _ she stayed up all night.
that
B、that; which
C、what; that
D、what; as