—Is Mike a diligent student?  —No，but he is a lazy one，if   ___         ．

This book teaches us how to analyze _______is causing the stress in our lift.

—Who’s that at the door?—          is the milkman.

Some friends tried to settle the quarrel between Mr. and Mrs. Smith without hurting the feeling of _____, but failed.

----- Is there anyone who is going to the Great Wall?  ----______ .