I want to know how long ___ when you get there.a.the film had been on b.the film had lasted

题目

I want to know how long ___ when you get there.a.the film had been on b.the film had lasted
为啥？

答案

A
因为A：我想知道等你到达的时候电影已经上映了多长时间（电影已经演到哪了）
B：我想知道等你到达的时候电影已经持续多长时间了
个人认为A是比较合适的.