This is _______ difficult problem that few students can work it out. [ ]
Is Mike at home? — No. He ________ with his friends now.
What _____ useful book! And _____ book is popular with students.
Do you know the famous writer Moyan ______ has got the 2012 Nobel Prize?— I feel proud of him.
_______ for your step, Jim, or you might fall into the lake. – Well, I got it．