—What have you learned from your experience in Thailand?—Well, meeting people from another culture ______ be very difficult．

Mum prepares breakfast for us every morning, so she __________ early.

—What do you think people can do for their aged parents?—They_________ do anything except to be with them and be themselves. 

Please do not feed the fish; they _____ die if they eat too much.

–Look at that girl! Is it Susan? --No, it _______ be her. She has gone back to her hometown.