单项选择题
A．a worthless burden to big cities B．something that can be reused C．a raw material for making new products D．able to be recycled but difficult to handle
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.