the morning of June 25 they visited the factory.In B. On C. At D. From

问题补充：

the morning of June 25, they visited the factory.

In B. On C. At D. From

答案：

解析：考查介词，在具体某一天应用On，题中句意为在六月二十五日的早晨，他们参观了这个工厂。故选B。