句子（1）：  China and Italy signed a memorandum of understanding  on jointly advancing the construction of the BRI , making Italy the   

                      first member of the Group of Seven to join the initiative.

句子（2）： The two countries have laid a solid foundation for BRI cooperation.

句子（3）： Besides , China and Fance concluded agreements on the third round of the BRI-related demonstration projects in third-

                     party markts and launched a third-party market fund during Xi's state visit to France this March.

问：   the BRI= the Belt  and  Road  Initiative : "一带一路倡仪" ，  按照冠词语法，由普通名词构成的专有名词其前要用定冠词the . 句子1）

          中其前用了the ,这是没有问题的，然而在句2) 中BRI前却没有用the , 句子3) 中BRI前却又有用the，请问这其中的语法原理和规则到底

          是怎么规定和使用的？此3句中the的用法为什么不同？