The bed is the one ____ ___ he slept.这里要填什么关系代词或副词

The bed is the one ____ ___ he slept.这里要填什么关系代词或副词
The bed is the one ____ ___ he slept.这里要填什么关系代词或副词

The bed is the one ____ ___ he slept.这里要填什么关系代词或副词
in which

in which.

when is