这里的this platform 和 the platform有区别吗？各位大神

Question

In 1858, a French engineer, Aime Thome de Gamond, arrived in England with a plan for a twenty-one-mile tunnel under the English Channel. He said that it would be possible to build a platform in the centre of the Channel. This platform would serve as a port and a railway station.

Answer 1

这里只能使用 this platform ，而不能使用 the platform 吧，因为要与前面的 to build a plaform 关联起来，表示是前面提到的平台，用 the 说明不了这点。

Answer 2

In 1858, a French engineer, Aime Thome de Gamond, arrived in England with a plan for a twenty-one-mile tunnel under the English Channel. He said that it would be possible to build a platform in the centre of the Channel. This platform would serve as a port and a railway station.
1858年，一位名叫埃梅.托梅.德.干蒙的法国工程师带着提出一个计划，那就是建造一条长21英里穿越英吉利海峡可以到达英国的隧道。 他说在英吉利海峡的中心建造一个平台是可能的。 这个平台将用作港口和火车站。