根据首字母提示，联系上下文，完成短文。

Do you know Hong Kong? Hong Kong is a city of China. It came back to China from the UK on July 1st in 1997. People in mainland (大陆) d on the right side of the road. But it is different in Hong Kong. You must be very c because cars move on the l . In the morning and in the evening when people go to or come from work, the streets and roads are very b, but the traffic is not very bad. Because they all follow the traffic rules.