用同样长的小棒搭正方形,想一想,最少要几根?
搭1个 搭2个 搭3个 搭4个
4根 ____根 ____根 ____根
已知a为非负数,则下列各式中正确的是( )
The old man lives _____ in a ______ house, but he doesn't feel_____.