1. I tripped over a root and scraped my knee.2. When I was walking down the street, I slipped on a banana peel and fell on the ground. Thankfully I was alright.
 trip over/on something slip on something falltrip over/on something = 採到什麼而跌跤slip on something = 採到什麼而滑倒fall 指實際的倒下的動作。
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.