The correct answer to this question is alternative D) "Coalition air strikes caused civilian casualties."
During the Afghan war, there were several battles and attacks both by land and air. Just like any other armed conflict there were casualties on both sides, but Afghan casualties might have caused some of the Afghan people to turn against the United States.
Other Americans improved and publicized the Santa Fe Trail as of 1822, in order to take advantage of new trade opportunities with Mexico. It had just won independence from Spain in the Mexican War of Independence.