Excuse me, may I borrow your Chinese-English dictionary— OK, here you are. But you can it for only two days．

The research is so designed that once ______ nothing can be done to change it [ ]

My mom once worked in a very small village school, which is _____ only on foot. [ ]

Could Daisy solve that difficult physics problem by _________

It’s an _______ book, I am _______ in it.