问题
单项选择题
This new method not only saves time but also saves energy（）operating on two batteries instead of four.
A.in
B.by
C.on
D.for
答案
参考答案：B
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This new method not only saves time but also saves energy（）operating on two batteries instead of four.
A.in
B.by
C.on
D.for
参考答案：B