____ was invented in 1917.
举一反三
- In 1917, The U.S.Rubber Company invented sneakers.
- If computers ______, many problems on space flight could not have been solved. A: had not been invented B: are not invented C: were not invented D: have not invented
- 57. James watt ____ the steam engine. A: was inventing B: invented C: had invented D: has invented
- When was the first bicycle invented The first bicycle was invented .
- An American_______the bicycle. A: is invented B: invented C: invents