－ Look! Mrs Green is wearing a black dress today.－ I think she _______ wear red. She looks young in red.

–Must I return the story book tomorrow, madam?       –No, you ______ bring it here next Monday.

---Isn’t that your teacher over there? ---No, it ______ be him. I’m sure he doesn’t wear glasses.

The manager commanded that the work ____ finished by the end of this month. 

 Don't use water to put out the fire if oil catches fire. As is known, oil ________ float on water.