发绀是窒息的共同表现，其中以（）、（）、（）处为明显。
参考答案：面部；指甲床
Mary is said _____ in the supermarket for 5 years, but I don't know why she resigned last month. [ ]
A. to have been working
B. work
C. to be working
D. to have worked
农业在社会主义国民经济发展中起( )作用。
A．决定
B．主导
C．稳定
D．基础
