1. Rear tires wear out easily.2. After fifty thousand miles on the road my car tires are worn out.3. Bald tires4. If you grind your teeth during sleep you'll need to wear a nightguard.
 wear out bald grind
這是一個連環問題: 燃燒石油導致二氧化碳增加，二氧化碳增加導致溫室效應，溫室效應導致冰層融化、海平面上升。 (請填空)
This is a chain of problems. Burning oil leads to increase in carbon dioxide, which leads to the geenhouse effect, which leads to melting of glaciers, which leads to rising sea levels.