B）下列5题中的句子可以组成一篇小短文，请从所给的四个选项中选出可以填入空白处的最佳答案。（答案涂在答题纸上）
Faraday made the ________ electric motor in 1821. It was an invention that used electricity to produce movement.
A. obvious          B. social        C. mad            D. first