A：
B：
C：
D：
已知一元二次方程ax2+bx+c=0，若a+b+c=0，则该方程一定有一个根为（ ）
It took us half an hour ____ (find) out the cost by train.
—______ did you play computer games just now?
—Two hours.
我会数，我会填。
山共有____画，笔顺是____。
