They were surprised that a four-year-old boy should work out such a difficult problem ____ they themselves couldn’t.
---How long _______ each other before they ________ married ? ---For about a year .
I really wonder ______ he has posted me many parcels _____ we worked together .
It is a rule in his family that ______ comes home earlier should cook the dinner for the family .
The duties of a policeman are _____ than ____ .
The black horse is _____ of the pair .