Fill in the blanks with the words or phrases given in the box. A. folding B. hazardous chemicals C. Pets D. regulations E. skateboarding F. smoke Shanghai Metro has its to keep travelers safe and comfortable. First, riders may not spit, , drink alcohol, leave litter or draw graffiti in stations or on the trains. Second, some articles are forbidden on the subway, such as weapons, explosives, flammable items and . and bicycles, including bicycles, are not allowed, either. Third, passengers are prohibited from dangerous behavior, such as roller skating or in the stations or on the trains. A. B. C. D. E. F.