A:红磷和白磷
B:金刚石和石墨
C:氧气和臭氧(O3)
D:二氧化硫和三氧化硫
Let me i____a new way of learning Chinese to you.
---Jenny,will you leave for the USA now?
---No. It will be two weeks________I leave here.
已知关于x的一元二次方程(a-1)x2-x+a2-1=0的一个根是0,那么a=____ .