Potatoes can provide about one-third of our daily (require) ________ of Vitamin C. （词形转换）
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After she had the report (type) ________, she put it on the director’s desk. （短语结构）
If you had asked him again, he might (change) ________ his mind. （虚拟语气）
()不是造成数控系统不能接通电源的原因。
A. RS-232 接口损坏
B. 交流电源无输入或熔断丝烧损
C. 面铣刀
D. 直流电压电路负载短路
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