Todayrocketsarevery56

問題詳情：

   Today rockets are very 56________ (advance) machines  57        we can use to send astronauts into space. They are also used in firework displays 58                  (celebrate)       

great events. It is said59      rockets were probably invented60     accident about 2000 years ago.

【回答】

56. advanced  57. Which/that   58. to celebrate    59. that    60. by

知識點：語法填空

題型：未分類