It ultimately depends on personal preference and what you would use more often. If you find yourself needing a pen frequently, then a pen would be the more practical choice. However, if you are someone who frequently loses or misplaces keys, then a keychain might be the more useful option. Both items can be functional and stylish accessories, so it's really a matter of what you would get the most use out of. **

Without further information or context, it is difficult to determine if the keychain is broken. If you can provide more details about the issue with the keychain, such as a description of the damage or malfunction, I would be happy to help assess the situation. **

There are many different bicycle thermometers available on the market, so the best one for you will depend on your specific needs and preferences. Some factors to consider when choosing a bicycle thermometer include the type of display you prefer (digital or analog), the mounting options available, the temperature range it can measure, and any additional features such as a built-in compass or backlight. It's also important to consider the durability and reliability of the thermometer, especially if you plan to use it for outdoor activities. Researching and comparing different models will help you find the best bicycle thermometer for your needs. **

To mount a compass attachment onto a compass, first ensure that the attachment is compatible with the specific model of compass. Then, carefully align the attachment with the designated mounting area on the compass. Depending on the design, you may need to use screws, adhesive, or other fastening methods to secure the attachment in place. It's important to follow the manufacturer's instructions and make sure the attachment is securely mounted to ensure accurate readings. **

A car keychain is a small decorative item that is attached to a set of car keys. It is often used to personalize and accessorize the keys, and can come in various designs, shapes, and materials. Some keychains may also have additional functions, such as a mini flashlight or a bottle opener. Overall, a car keychain serves as a practical and stylish way to keep track of and identify one's car keys. **

This keychain is a multi-functional tool that can perform a variety of tasks. It includes a bottle opener, a screwdriver, a wrench, and a ruler, making it useful for everyday tasks and emergencies. Its compact size and lightweight design make it easy to carry around and have on hand whenever needed. Overall, this keychain is a versatile and practical tool for anyone to have. **

Yes, a thermometer can break if it is mishandled or dropped. The glass casing of a traditional mercury thermometer can shatter if it is subjected to impact or extreme temperature changes. Digital thermometers can also break if they are dropped or exposed to water or moisture, causing damage to the electronic components. It is important to handle thermometers with care to prevent breakage and ensure accurate readings. **

No, the thermometer has not burst. Thermometers are designed to measure temperature and are typically made of materials that can withstand the range of temperatures they are meant to measure. If a thermometer were to burst, it would likely be due to extreme conditions or damage to the thermometer itself. **