Oh, you have a headache and a cough. __________ have you been like this? —Two days.[ ]

My father ______ me my first model car ten years ago.

hat do you think of genetically modified food (转基因食品)? —We all think ______ is careless ______ some scientists to say it is safe before doing any experiment.

The littleboy’s mother told him she would be back___ an hour,but she didn’t. [ ]

Look at the sky! What is it?—Oh! _______UFO is landing on the ground.