________ is no possibility ________ she can finish the task in two hours.　　

I didn’t know when he     back. He said he would call me when he     home.

 ______ piano is her main focus, she's also great at guitar.

—How unhappy your roommate looks!—Yes, but he's not willing to tell me what it is _______ is troubling him.

If there       no buying and selling of animals, there      no killing in nature.