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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Heart Attack In the United States, and especially in big cities and rural areas, tens of thousands of people with hearts that should be good 【51】 to keep them alive die each year for lack of adequate ...
A.
by
B.
to
C.
and
D.
toward
【多选题】多人合用一台车床时,旁观者应注意()
A.
站在操作者身边,帮助其注意切削情况
B.
站在操作者右前方45°角的安全区域
C.
禁止站在卡盘及切削点的正前方
D.
站在操作者正对面,帮助其清理铁屑