某汽车企业原来生产高档汽车产品，后来决定增加低档汽车产品，这种产品组合策略是（）
A、向上延伸
B、向下延伸
C、反向延伸
D、缩减产品组合
参考答案：A
图像的彩色显示主要有两种方法，（）和（）
______ of his time ______ been spent on studies every day.
A．Four-fifths; has
B．Four-fifths; have
C．Four-five; has
D．Fourths-five; have
