工程项目按投资效益和市场需求划分为（）。
A．竞争性项目
B．政府投资项目
C．基础性项目
D．非政府投资项目
E．公益性项目
参考答案：A, C, E
生态脆弱区
— What's the matter with you?
— Oh, I'm feeling tired and sleepy now. I _____ so late last night. [ ]
A. couldn't have stayed up
B. mustn't have stayed up
C. shouldn't have stayed up
D. needn't have stayed up
