区别in the hospital 和at hospital

题目

区别in the hospital 和at hospital
her husband is badly ill,so she is _______now.
a.in hospital b.in the hospital
c.at hospital d.at the hospital
我觉得该是in the hospital,可答案是at hospital ...
为什么啊 at hospital 和at the hospital 和in连接的有什么不一样啊
没有一个人说清楚了的

答案

in hospital,住院
at hospital,在医院工作
in the hospital,在医院里面某处
at the hospital,在医院（不一定是里面某个地方）