亚历山大·格拉汉姆·贝尔发明了电话。
Alexander Graham Bell ___invented the telephone.
计算机是在20世纪发明的。
The computer was ___invented in the 20th century.
她正在为科学展发明一种新型机器人。
She is ___inventing a new type of robot for the science fair.
他们是什么时候发明个人电脑的?
When did they ___invent the personal computer?