100℃ is the temperature ___ which water will boil[ ]

Mary _______as a secretary in this company for twenty years and now she stays at home taking care of her own garden.

“Why can’t you do it now” “_____I’m toobusy.”

What _____ does he like best — He likesrunning.

Not only you and I but Peter, the top student in our grade, ________ not able to solve the problem[ ]