-How about having a picnic with me?-I’d love to, ______ I’m afraid I have no time. A. so B. and C. but
________ my surprise, the twins have nothing _______ common.
---Do you know sound travels very fast?----Yes. But light travels _______ sound.
Paper-making is one of _______ of ancient China.
Could you please give some _______ to the _______ teachers?
Please wait here. I’ll be back in _______ hours.