A：加法的交换律
B：加法的结合律
C：加法的交换律和结合律
D：以上均不对
— Can you believe _________ little children can finish the difficult problem in _________ a short time?
— I can't believe it until I see it with my own eyes.
It's going to ____ (rain) tomorrow.
第一个五年计划取得巨大成就____第一汽车制造厂生产出第一辆汽车，____长江大桥建成，连接了南北交通。
- My mother is ill.
- ______________.
