沥青碎石属于骨架-空隙结构，具有较好的高温稳定性，但耐久性较差。( )
参考答案：对
将1299万保留三位有效数字为______．
用所给单词的适当形式填空。
1. Simon said he had a _______( please) journey last week.
2. Every year many _______( tour) come to Beijing to visit the Great Wall.
3. We should work hard at English because it's important in our_______( day) life.
4. It is_______ (possible) for him to finish the work in one hour, because it's very difficult.
5. Don't worry! They can take care of_______( they).
