被西欧人称为“绿色金子”的是[ ]
A．奶牛
B．小麦
C．牛奶
D．牧草
答案：D
互补品(complementary goods)
— are you going for vacation?
—I'm going to Australia in March.[ ]
A. when
B. When and where
C. How
D. Where and when
