In first sentence we r paying emphasis on free trade. In second sentence we saying that free trade is losing its shine… How does this make sense?
In the first sentence the main point of focus was free trade(major importance was given to it) . Now, in the second sentence we’re saying that free trade is losing something _____(i.e. now free trade is not of major importance, losing it’s importance ). Hence, we’re looking for a words which conveys this idea.
Now , irrelevance is out as it saying the opposite of our idea , rhetoric means the art of speaking or writing effectively( out of topic ), hence , by using POE(process of elimination) you’re left with Burnish . Now, sometimes it may not exactly be the word we’ve guessed but our job is select the best choice out of the given options .
According to me:
Shine in-here is used in sense of giving importance . For eg: Cristiano Ronaldo was the shining star of Real Madrid, but now he has lost his shine. Here, "lost his shine " means that Cristiano Ronaldo, is not as impressive or brilliant as he used to be. It implies that his level of performance or charisma has diminished, and he is no longer shining as brightly as he once did.