在氧气炼钢时烟筒外排的红褐色浓烟都是()。
A.氧化铁细粉导致的
B.因炼钢时粉尘浓度过大而引起的
C.二氧化铁细粉导致的
D.因炼钢时粉尘浓度过小而引起的
参考答案:A
句型转换。
1. Let's have dinner. (改为否定句)
Let's_____ ______dinner.
2. What can I do for you?(同义句)
Can I ______ ______?
3. Those are rulers. (改为单数形式)
______ is a ______.
4. His brother has a computer. (改为一般疑问句)
________his brother a computer?
5. Your ID card is on the dresser. (对划线部分提问)
______ is ______ ID card?
简述RH循环工作原理。