工程质量事故的特点有（）。
A．复杂性
B．隐蔽性
C．严重性
D．波动性
E．多发性
参考答案：A, C, D
若斜率为-3的直线经过坐标原点，则该直线的方程为 [ ]
A.x-3y=0
B.3x-y=0
C.3x+y=0
D.x+3y=0
It was an__________ night. I was very ________ that night. [ ]
A. exciting; exciting
B. excited; exciting
C. exciting; excited
D. excited; excited
