选出不同类的一项
- Sun Yang is ________a talented swimming player.
-That's right. He did best in Barcelona(巴塞罗那)in August, 2013.
如图所示,用等大反向的力F和F′压住两块木板,中间夹着一个重量为G的立方体金属块,它们一起处于静止状态.则( )