用反证法证明：“若整数系数一元二次方程ax2+bx+c=0（a≠0）有有理根，则a，b，c中至少有一个是偶数”，下列假设中正确的是（ ）
补全对话。
A: ____?
B: I'd like some fish and rice.
A: OK. Hold on, please.
B: ____?
A: Fifty yuan, please.
B: That's OK. ____.
In many places in China, the old over 90 ____ (take good care of) not only by their family but also by the government.
⑴ ____ ⑵ ____⑶ ____
