The student on duty helps the teacher erase the blackboard when asked to.
the student on duty問今天誰是值日生只要說 Who's on duty today? 即可
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 greenhouse effec, which leads to melting of glaciers, which leads to rising sea levels.