B.điền từ vào chỗ trống
signals and installed to lights of
Modern traffic (1)………………..are an American invention. Red-green systems were (2)……………. in Cleveland in 1914. Three-color signals were installed in New York in 1918. They used (3)……………… be operated by hand from a tower in the middle of the street. The first lights of this type appeared in London, on the junction between St. James Street (4)………………Piccadilly, in 1925. Automatic signals were installed a year later.
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Sinh Học lớp 12
