Now the computers are ________ more and more people all over the world.

A．used for

B．discovered by

C．used by

D．discovered for

下列各组物质中，无论以任何比例混合，其混合物中碳的百分含量不变的是

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A．一氧化碳和乙烷

B．乙烯和CH₃CH=CH₂

C．乙烯和乙炔

D．甲烷和乙炔