— You were not in when I dropped in on you yesterday evening.

— Oh, so sorry. I ____ at the railway station for my sister from Beijing. [ ]

A. waited

B. had waited

C. was waiting

D. have been waiting

总胆固醇酶法测定中，最后使用的酶是（）

A.胆固醇酯水解酶

B.过氧化物酶

C.胆固醇氧化酶

D.脂蛋白脂肪酶

E.过氧化氢酶