, it began to run unexpectedly. A. While cleaning the machine B. To clean the ma
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______, it began to run unexpectedly.
A. While cleaning the machine B. To clean the machine
C. He was cleaning the machine D. While he was cleaning the machine
试题答案
D
如果用现在分词作状语，其逻辑主语应与句子主语保持一致。A项不符合这一要求；C项与后一分句之间缺少连接词。