The answer is option D: "It is for this reason that I wish to introduce today a proposal that has been before every Congress for the last 40 years."
The statement best exemplifies the use of formal language because, to begin with, it is a complex sentence. In fact, it is a cleft sentence which begins with it to emphasize what comes next. Secondly, there is no ellipsis and vocabulary reflects the choice of longer words than in informal speech. Finally, the use of passive voice is typical of formal registers.