如果（）氢化，则（）中断，故二氢黄酮醇（）色。
参考答案：双健；交叉共轭体系；无
________ for several weeks，the city needed food.
A．As having flooded
B．Being flooded
C．Having been flooded
D．To flood
该提单正本仅有一份。（）
