已知a2+a=1,则代数式3-a-a2的值为____.
A:What's the matter?
B:I have ____ ____.
A:I'm sorry to hear that.____ ____.
B:Thank you.
可逆反应A(g)+3B(g)⇌2C(g)+2D(g)在4种不同情况下反应速率分别如下,其中反应速率v最大的是( )