根据汉语意思完成下列句子
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.