Answer:
Although the sentence is not underlined on your question, I'm assuming the underlined portion is sentence [6] because it seems out-of-place.
Sentence 6 strays away from the main point of the paragraph, that:
"Henry David Thoreau... crafted an entire essay on the values of civil disobedience, and those opinions can be seen throughout the 20th century."
Sentence 6 describes a personal story about museum shirts, which really does not any essential information to the paragraph.
So, my guess would be A, since it detracts from the clear line of reasoning established in the paragraph.