The senior police officer has been continually exposed to the underbelly of society and eventually got killed.
 underbelly underworldunderbelly 跟 underworld 都形容一個社會較黑暗較多犯罪的一面
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 problms. Burning oil leads to increase in carbon dioxide, which leads to the greenhouse effect, which leads to melting of glaciers, which leads to rising sea levels.