在热网系统全停时，加热器水侧与汽侧分别充入（），用来防止腐蚀。
A.氮气、压力水
B.压力水、氮气
C.低压水、高压水
D.软化水与蒸汽
参考答案：B
句型转换。
1. Mr Turner found his ticket yesterday evening. (改一般疑问句)
Mr Turner his ticket yesterday evening?
2. Was the boy born in America? (改陈述句)
The boy in America.
3. Joan stayed in the park for 3 hours last Sunday. (就划线部分提问)
Joan stay in the park last Sunday?
4. Mike had a busy day yesterday. (用tomorrow改写)
Mike a busy day tomorrow.
5. Jim was born in 1982. Li Lei was born in 1982, too. (改同义句)
Jim Li Lei born in 1982.
为预防胎儿的神经管畸形，妇女在怀孕前一段时间及怀孕期都应注意补充（）.
A.维生素B1
B.维生素B2
C.叶酸
D.维生素D
