Overheadbridgesarefoundinmanypartsofbigcities,especiall...
问题详情：Overheadbridgesarefoundinmanypartsofbigcities,especiallyinplaces___46___trafficisveryheavyandcrossingtheroadisdangerous.Thepurposeofthesebridges___47___(be)toenablepedestrianstocrossroads___48...