根据路线图，补全短文。（每空一词）

Mary and Cindy are at the subway station. First, they should at the shopping mall. Then they should . They must pay attention to the traffic lights at the first . They should and wait at the red light. After walking for some minutes, they will see the science museum the supermarket. When they go back to the subway station, they should at the shopping mall. It's also a good way to travel around the city subway.