Let's look at the context for both of these quotes. The author quotes the current language in the UN charter (lines 8-11) and then notes that there were members who felt this language was not strong enough (lines 11-15). This group then lobbied for a stronger language advancing a proposal quoted in lines 20-22 in contrast to the language in the charter on lines 8-11. Thus we can infer that these two quotes serve to compare and contrast the strengths of the language in the Charter and the alternative proposal (B).
Let's see why the other answer choices are wrong.
(A) to contrast the different definitions. It is true that the two quotes contrast two documents but there are no human rights definitions involved, the quotes show the contrast between countries' obligations
(C) to identify a bureaucratic vocabulary that is common The context for these quotes implies the intention of the author to highlight the differences not to identify common elements.
(D) to highlight what the author believes to be the most important point in each document. This is an unwarranted inference, nowhere does the author suggest that these are the most important points in each document.
(E) to call attention to a significant difference in the prose styles The quotes do call attention to the differences but in the strength of the human rights language and countries' obligations rather than the prose style.