she was able to give the police a full account of since she had been ___to it.选哪个?
问题描述：
she was able to give the police a full account of since she had been ___to it.选哪个?
A:an observer
B:a witness
答
B:a witness目击证人为什么答案是A呢？an observer观察者我知道那是神马意思，我想知道为什么答案选A