Other countries had built underground railways before the Metropolitan line opened.

Other countries had built underground railways before the Metropolitan line opened.
正确答案：False
答案解析：The Metropolitan line was the world's first underground railway. So no other countries had built underground railways before it opened. It was a pioneer in the development of underground railway systems. （大都会线是世界上第一条地铁。所以在它开通之前，没有其他国家修建过地铁。它是地铁系统发展的先驱。）