单羟基黄酮类酚羟基酸性最弱的是()。
A.5-OH
B.7-OH
C.9-OH
D.11-OH
E.41-OH
参考答案:A
—I'm too tired to walk any farther. Let's stop ________.
—Good idea![ ]
A. have a rest
B. to have a rest
C. having a rest
D. had a rest
厂区各类横穿道路的架空管道及通廊,应标明其()及()。