Must we keep the window _______ all the time—No, you don’t have to.

The police found that the house____and a lot ofthings___.[ ]

It has been announced recently that all the schools ________ not have the students attend school if thestudents have high temperatures.[ ]

I’ll never understand how it _____ that he still insisted on going there alone after being told about thepossible danger.[ ]

Although he is very old, ______ he works very hard