---What did Jack ask you just now?

--He wanted to know how long ________ when I reached the cinema.

A．had the film been on

B．the film had started

C．the film had lasted

D．had the film ended

肝素抗凝作用的主要机制是（）

A.直接灭活凝血因子

B.激活血浆中的AT-Ⅲ

C.抑制肝脏合成凝血因子

D.激活纤溶酶原

E.与血中Ca²⁺>络合