21. There used to be fewer people and __________ on the roads. A. roofs B. helmets C. helicopters D. vehicles 22. Do you know the __________ in the UK is to keep to the left? A. traffic light B. traffic rule C. traffic jam D. speed limit 23. It is dangerous to ride a motorbike without a __________ A. helmet B. triangle C. tricycle D. circle 24. In Hanoi, during rush hour, some road users ride their motorbikes on the __________ A. driving licence B. lane C. pavement D. seat belt 25. Traffic is terrible during the __________ when everyone is in a hurry to get to work or come back home. A. traffic light B. road sign C. traffic rule D. rush hour 26. The __________ for motorcycles is 40 km/h in towns and 60 km/h outside urban areas. A. speed limit B. driving licence C. traffic rule D. traffic light 27. You must __________ the traffic rules in order to avoid accidents. A. park B. obey C. reverse D. warn 28. It takes us more than three hours to drive across those __________ roads. A. wide B. safely C. right-handed D. bumpy 29. You need a driving licence to __________ A. drive a car B. ride a bike C. get on the bus D. get off the train 30. The large supermarkets in Vietnam often let you __________ free. A. park B. obey C. warn D. find