I would definitely say B.) A smile because if you were just staring it may be rude or distracting to the speaker and a smile shows you are listening and absorbing the knowledge
Answer:
a controlling statement, like a claim
3 and also that looks just like my old computer. is it a notebook2000? windows 8.1?
you know more that the normal amount of knowledge you need to know or you are really good at something so it is easy for you to explain it to someone