摘要：24．What happened when Mr. White called out "Who is there"?A．Nobody answered． B．Two boys came out． C．The boys stopped talking．
网址：http://m.1010jiajiao.com/timu_id_800865[举报]
Of all the inventions, what do you think is ________ invention in the 21st century．
- A.the most helpful
- B.more helpful
- C.helpful
- D.more and more helpful