依靠市场机制的自发运行，时常会出现失业、经济失衡和（）A、成本上升 B、停产 C、产量下

若x=±1是一元二次方程ax²+bx+c=0的两根，则（　　）

A．b=0，a+c≠0

B．b≠0，a+c=0

C．b=a+c=0

D．a+b-c=0

A．She is trying to persuade the man to attend the rock-climbing class.

B．She is trying to tell the man many students are interested in it.

C．She is trying to tell him the college doesn’t have any rock-climbing equipment.

D．She is trying to tell him there are no appropriate places for rock-climbing nearby.

将甲、乙两种金属的性质相比较，下列不能说明甲的金属性比乙强的是（　　）

A．甲与水反应比乙与水反应剧烈

B．甲单质能从乙的盐溶液中置换出单质乙

C．与某非金属反应时甲原子失电子数目比乙的多

D．甲的最高价氧化物的水化物比乙的最高价氧化物的水化物碱性强

治疗痉挛的适当理由是（）

A.体位的摆放严重困难以致皮肤破裂

B.Ashworth评级大于Ⅱ级

C.脑卒中后下肢伸肌痉挛

D.胸段脊髓损伤后阵挛

E.防止中枢性疼痛的预防性治疗