如果|x|+||x|-1|=1，那么（ ）
A．（x+1）（x-1）＞0
B．（x+1）（x-1）＜0
C．（x+1）（x-1）≥0
D．（x+1）（x-1）≤0
当x≤-1时，原等式化为，-2x-1，不成立；
当-1＜x≤0时，原等式化为，x-x+1，成立；
当0＜x＜1时，原等式化为，-x+x+1，成立；
当x≥1时，原等式化为，2x-1，不成立；
故-1≤x≤1，∴（x+1）（x-1）≤0，
故选D．
A
小题1: We can see ________ pencils in Liu Jun’s bag. A. one B. two C. three 小题2:Zhang Yuanyuan’s knife is ________. A. pink B. blue C. white 小题3:_________ has a map in his bag. A. Chen Xiaofeng B. Liu Jun C. Meng Yi 小题4: Meng Yi has __________ in his bag. A. a pen B. a ruler C. a cake 小题5:_______ and ______ both have some (一些) books. A. Liu Jun, Zhang Yuanyuan B. Zhang Yuanyuan, Meng Yi C. Liu Jun ,Chen Xiaofeng |