A:斯大林
B:赫鲁晓夫
C:勃列日涅夫
D:戈尔巴乔夫
命题“∀x∈R,x2-x+14≥0”的否定是( )
①没有给试管均匀受热; ②试管外壁潮湿; ③试管口没有略向下倾斜;
④忘了加棉花; ⑤加热时试管底部与灯芯接触; ⑥收集完氧气,先撤酒精灯.
从方框中选择正确的词,补全句子。
closed, fly , share , sheep, popular
(1) I often see some children____ kites in the park at weekend.
(2)Yao Ming is ____ with young people.(3)We____the world with plants and animals.(4)The bookshop is ____ at this time everyday.(5)My uncle keeps many____ on his farm.