______ of that country _______ by snow.
A：Second thirds; is covered
B：Two thirds; is covered
C：Two thirds; are covered
D：Two third; covers
一个质量为m的质点以速度v0做匀速直线运动，某时刻开始受到恒力F的作用，质点的速度先减小后增大，其最小值为 3v02 ，质点从受到恒力作用到速度减至最小值的过程（ ）
氢气和氧气的混合气体共10g，点燃后恢复到室温，经测定还剩下氢气1g，混合气体中含有氢气 ____ g，氧气 ____ g．
