Science and technology are developing ______ quickly that some new electronic products are out-of-date within several months.
The coat is very nice. Can I ______?
Is this your MP3, Kathy?— No. ______ is in the bag.
Listen! Is that Pingping playing the guitar? —No. It __________be Pingping. He has gone to Beijing.
Mary is the _________ child of her parents.