理解问题的第一步是建立问题空间的内部表征。
参考答案：对
– I have got a headache.
--No wonder. You ___in front of that computer too long.
A．work
B．are working
C．have been working
D．worked
减温减压系统停运操作时，应该快速关闭减压阀前手阀。（）
