A:which I think is.
B:which I think it is.
C:which I think it.
D:I think which is.
保持愉快心情是中学生心理健康的核心.当遇到压力时,不宜采取的调节方法是
已知关于x的方程x2+bx+a=0有一个根是-a(a≠0),则a-b的值为( ).