One of the MOST famous opponents of the War with Mexico, whose actions

One of the MOST famous opponents of the War with Mexico, whose actions became a model of civil disobedience for years to come, was

A) John C. Frémont, the California explorer.
B) John L. O’Sullivan, editor of the Democratic Review.
C) Henry David Thoreau, American poet and author.
D) Jefferson Davis, future president of the Confederacy.

ANSWER
Answer: C