单项选择题

In the process described by the woman, why is the c0al burned

A．To produce a gas containing carbon and hydrogen.
B．To remove impurities from methanol.
C．To heat the reactors.
D．TO prevent dangerous gases from formin

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单项选择题According to the man, how do some bees use their sense of smell

A．To find their way back to the nest.
B．To locate plant fibers.
C．To identify kinds of honey.
D．To identify relatives.

单项选择题Why was the man worried at first

A．He couldn't decide on a topic for his paper.
B．He thought his paper was late.
C．He hadn't heard from his family in a while.
D．He thought the woman had been ii