题目内容：

    Bicycles share the road with cars and t1.. Drivers do not always n2. bicycles. So bicycle riders must pay a3. to the traffic around them and know traffic signals. They must know and obey the safety rules. They must wear helmets to protect their heads. When r4. at night, they must wear light-colored clothes, and have lights in the front and reflectors on the back of their bicycles. A bicycle accident may be serious. In c5. of an accident, bicycle riders should know how to give first aid. If an injury is serious, they must call 120 for help. In a word, the best way to be safe is to be careful.