硫磺制酸装置火管锅炉汽包内过滤网的作用有（）等。
A.稳定锅炉液位
B.稳定锅炉压力
C.实现和改善汽水分离
D.过滤炉水水渣
参考答案：C
"Opt-out" mechanism is probably ______
A．a machine that can be attached to your computer
B．a button that you can make a choice to read or not to read
C．a software that you can play a computer game
D．an e-mail that says some good words to you
箍筋的钩长规定为多少？
