1. 长城大约6 700千米长.
    The Great Wall is about __________ __________ __________.
2. 他现在太忙了,无法帮助你.
    He is __________ __________ __________ help you now.
3. 重要的是确保一切顺利.
    It's important __________ __________ __________ that everything goes well.
4. 树种得越多,沙尘暴就越少.
    __________ __________ trees we plant, __________ __________ sandstorms we will have.
5. 直到妈妈回来时,他才完成作业.
    He __________ __________ __________ __________ until his mother came back.

1. 我用了两个小时修车.
    It __________ me two hours __________ __________ the bike.
2. 直到妈妈回来时,他才完成作业.
    He __________ finish his homework __________ his mother came back.
3. 他和我都不是老师.
    __________ he __________ I am a teacher.
4. 他从小就对数学感兴趣.
    He became __________ in maths when he was __________.
5. 你最好乘火车.
    You'd __________ __________ a train.