The worried father is pacing back and forth outside the operation room as his daughter is undergoing a dangerous operation.
 pace back and forth walk back and forth walk to and frowalk 跟 pace 都可以指來回踱步.
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 effect, which leads to melting of glaciers, which leads to rising ea levels.