Final answer:
When riding a bike, you shouldn't hold a mobile phone, an umbrella, or a glass bottle. These items can distract you and impede your ability to safely control the bike, increasing the risk of an accident.
Step-by-step explanation:
While riding a bike, you should not hold items that can distract you or impede your ability to control the bike safely. The things you should not hold include a mobile phone, an umbrella, or a glass bottle. All of these items can take your hands away from the handlebars, potentially causing you to lose control of the bike and leading to an accident. Holding a mobile phone also distracts your attention from the road, which increases the risk of an accident. In contrast, to decrease radiation to the head, one should use a hands-free device, keep the mobile phone away from the body, and avoid using a cell phone in a car without an external antenna, but these precautions are for different scenarios and do not directly apply to bike safety.