小题1:cities
小题2:every/each
小题3:an
小题4:have used/ have been using
小题5:Besides
小题6:who/ that
小题7:in
小题8:polluted
小题9:importance
小题10:if / because
略
小题1:cities
小题2:every/each
小题3:an
小题4:have used/ have been using
小题5:Besides
小题6:who/ that
小题7:in
小题8:polluted
小题9:importance
小题10:if / because
略