单选题
An invention of an Italian professor
A、
gave later inventors the idea of moving air around in diving devices.
B、
can "clean" the air.
C、
was used to remove moisture.
D、
was nothing but a plan.
【正确答案】
D
【答案解析】
[解析]由第二段中的“The plan did not work，but...”可知答案为D。故应选D。
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