下列方程中,是关于x的一元二次方程的是( )
A:ax2+bx+c=0
B:x2=xx+1
C:1x2+x=3
D:4x2=9
My sister likes cartoons best. So she often spends a lot of time ________ TV in the evening.
已知AC为矩形ABCD的对角线,则图中∠1与∠2一定不相等的是( )