单项选择题
A．It throws away glass and sand from garbage. B．It collects heavy metal objects for selling. C．It separates garbage into useful and useless things. D．It pumps water into garbage and mixes it.
A．To describe an experiment in which a Hydrapulper is used. B．To introduce Hydrapulper, a new type of garbage disposer. C．To tell what the writer thinks of the recycling of garbage. D．To explain why garbage should be recycled in a new way.
A．their environment is becoming more and more dirty B．the traditional ways of treating wastes are not efficient C．they are short of useful materials D．they need new materials made from garbage