He has      for three or four days. 

—Look，your father is playing the piano over there.—He________ be my father. He has gone to Beijing.

My cell-phone  has disappeared. Who       have taken it away?

—We will go to the Wushan Square this afternoon, why not take a bus? —We ________ take a bus , it’s only one kilometer or more.

We _______ talk loudly when we see the sign “ Be quiet ”on the right.