Look, the set of keys _ _ on the teacher’s desk.

He worked ______ hard ______ he could pass the exam. [ ]

Can you please tell me something about life in the future?—Oh, maybe in the future, people will _______ by robots.

Could you tell the differences _____ these two words? — OK, let me have a try. [ ]

Sally is very happy. There is a big smile ______ her face. [ ]