To show that lightning was electricity, Franklin attached a metal key to a kite and flew it during a thunderstorm.

为了证明闪电是电，富兰克林把一把金属钥匙系在风筝上，然后在雷雨天把它放飞。

He tied a metal key and a strip of silk to the kite line.

他在风筝线上绑了一把金属钥匙和一条丝绸。