The refrigerator keeps food fresh; it was invented in the 1900s.

冰箱保持食物新鲜，它是在二十世纪发明的。

同一单元的其他句子

• When was the telephone invented?电话是什么时候发明的？
• The light bulb was invented by Edison.电灯泡是爱迪生发明的。
• Computers were invented in the twentieth century.计算机是在二十世纪发明的。
• Was the wheel invented in ancient times?轮子是在古代发明的吗？
• Don't touch the old machine; it was invented long ago.不要碰那台旧机器，它是很久以前发明的。