混凝土的碱性介质对钢筋有良好的保护作用，而混凝土碳化会使其碱度降低，故对钢筋的保护作用（）。
A.增强
B.减弱
C.不变
D.没影响
参考答案：B
句型转换。
1. The model plane is Nick and Peter's. (对划线部分提问)
_____ _____ the model plane?
2. Nick does the housework for his mother on Sunday. (一般疑问句)
_____ Nick _____ the housework for his mother on Sunday?
3. There's a kite in the tree. (对划线部分提问)
How many _____ _____ there in the tree?
4. Lily takes a walk after dinner every day. (划线提问)
_____ _____ Lily _____ after dinner every day?
5. She can go home at half past four. (对划线部分提问)
_____ _____ _____ she go home?
损伤颅脑的早期反应
A、肿胀；
B、缺血；
C、淤血；
D、充血
every day. (划线提问)