be long for 我没记错的话应该用主动的.I long to see you 就是我很渴望见你的意思 也就是 很渴望（sth.）=look forward to +sth/doing sth.
leave sb. to do sth. 就是让某人去做某事.
I left him to wash the windows. 就是我留他一个人去擦窗户.
I left him there washing the windows就是我留他一个人在那里,他正在擦窗户.
leave sth done 就是留下某样东西处于一个完成的状态.如He left those windows cleaned. 就是他走了,剩下那些已经擦干净了的窗户.
差不多就是这样的.