_____ of the water _____ polluted. We must try to protect our environment.

Who teaches ___ English?No one. I teach _____.

Is this ______ English book?—No. ______ is at home.

Mary is interested _____ volleyball, but she isn’t good _____ it.[ ]

John is in a bad mood these days. Do you know why?—His grandfather has just passed away. Let’s try to _______.