A:when does his son come back
B:when his son comes back
C:when his son come home
D:when his son came home
2 3 ,则 1a2 + 1b2 ﹣ a2b2 的最小值为____.
下表反映的是一种汽车行驶的路程和耗油量的情况.
一辆汽车2小时可以行驶100千米,平均每小时可以行驶____千米?
达到理解需要积极的沟通,这主要包括( )①真诚的赞美 ②坦诚的交流 ③细心的体会 ④主动的接近