— Jack, I call to tell you I have no time to attend your party next Friday. —What a pity!
A:am too tired
B:am too busy
C:am glad
根据题意填写下列空格
①商业贸易 ②人口迁徙 ③教育 ④外出旅游
如图所示,一个小球从高处下落到竖直放置的弹簧上并压缩弹簧向下做减速运动,忽略空气阻力,画出小球所受的重力G和弹力F。