Bruce _________his leg when he _____ in a football match yesterday afternoon.

A．broke; played

B．has broken; was playing

C．broke; was playing

D．was breaking; played

杨梅素的结构为（）

A．5,7,4′-三羟基黄酮

B．5,7,3，4′-四羟基黄酮

C．3,5,7,4′-四羟基黄酮

D．3,5,7,3′,4′-五羟基黄酮

E．3，5，7，3′，4′，5′-六羟基黄酮