____you stepped into the lab with your shoes on? You are supposed to take them off before you enter it.
British scientists said teenagers are programmed to take risks because they enjoy the thrill of dangerous situations________ others.
Everyone wants to live in a beautiful, comfortable and “livable ” place, but not ________ know where it is.
The comedy Tooth Fairy is based on the story all western children know: If a kid leaves a tooth under their pillow, they’ll receive a visit from the tooth fairy, who takes the tooth and leaves a gift ________.
Nearly four hundred supermarkets in Beijing are preparing to dim their lights ________ the "Earth Hour 2010" on Saturday night.
Younger adults who get either little sleep or a lot of it ________ see a greater expansion in their waistlines over time. A. mayB. mustD. needD. shall