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
