The boss ______ the worker how to do it, or the accident couldn’t have happened.

(2012·辽宁高考)One of our rules is that every student ________ wear school uniform while at school.

John, look at the time. ____ you play the piano at such a late hour?

 — When and where               we meet? — Let's make it 3:00 at my home.

  --- Whose hair band is this ?  ________ it be Kate’s ? --- I’m not sure . It ________ be hers.