— I phoned you at 7 yesterday evening but nobody answered.

— Oh, I _______my dog in the park then.

A．walked

B．was walking

C．had walked

D．would walk

线粒体中丙酮酸彻底氧化发生（）

A.3次脱羧，5次脱氢

B.2次脱羧，5次脱氢

C.4次脱羧，6次脱氢

D.3次脱羧，7次脱氢

E.4次脱羧，6次脱氢