We called the First-Aid Center ______ after the traffic accident happened.
A. immediately     B. shortly          C. quickly             D. hurriedly

答案为a,合适么？有人用c哪个更好从句子结构上来说，immediately 可以当做连词用，一……就，起到连接作用，可是后面有 after 二者可以放到一起用么？关键是 after 怎么理解？