用5%NaHCO3水溶液可从混合物乙醚液萃出的成分是()
A.4'-OCH3黄酮
B.5-OH黄酮
C.4'-OH黄酮
D.8-OH黄酮
E.7,4'-二OH黄酮
参考答案:E
He went there and has stayed there . [ ]
A. three days ago; for three days
B. for three days; three days ago
C. three days before; three days
D. before three days; three days before