The other day,my friend John drove his car down the street a

The other day,my friend John drove his car down the street at _ was a dangerous speed
The other day,my friend John drove his car down the street at _ was a dangerous
A.as B.which C.what D.that
如果题目是The other day,my friend John drove his car down the street at____I thought was a dangerous 毫无疑问是选 C ,但如果没有那个I thought 、选B吗