1. 飞机落地 it touches down on the ground
2. The increasing dropout rate is grounds for serious concern in the education system.
（辍学率上升是教育体系中值得严重关注的问题。）[某事/行为] + is/are grounds for + [行动],“是……的理由/根据/依据”. 常用于表示采取某种行动（尤其是负面行动，如投诉、解雇、处罚）的正当理由。
3.On the verge of
He is on the verge of crying, 强调临近重大变化
4. See somebody doing sth
英文中有一类都是这样的, 如hear, watch, notice, observe
5.限定性定语从句与非限定性定语从句的区别
去了从句,是否还能构成完整表达.The man who is wearing a red hat is my uncle.
My uncle, who is wearing a red hat, is very kind.
