—— It's no  easy task to catch a ticket on a website that receives l billion clicks daily．一一I can’t agree with you more．There      be errors for every single step

Mountain climbing ______ be really dangerous at times even though it is challenging and exciting in general.

It ________ be the postman at the door.It's only six o'clock.( 2011·江西)

—— Where is your father?  —— He has gone to the supermarket. He __________ at home.

It seemed that our nursery rhymes___ some magic because all the nights I sang them for my daughter, she would listen to them with keen pleasure．