Read this ! and answer the question: )

according to president regan's secretary of defense, the united states should only take on wars that the public would support and clearly could be won. this was the "lesson" of
vietnam. this strategy was reflected in the cautious approach used by the clinton administration after events in somalia. whenever the question of intervention in overseas wars came up, the united states stayed away or limited its participation to the use of aircraft. even when us embassies in tanzania and kenya were attacked by al-qaeda in 1998, the united states still did not act directly. instead, us forces launched missiles from hundreds of miles away in an unsuccessful attempt to eliminate bin laden.

based on the reading, what was the "lesson” of vietnam?

a. the united states was determined to win a conflict at all costs.
b. the united states was unlikely to commit troops overseas, even if provoked.
c. the united states favored isolationism, and refused to respond to overseas conflict in any way
d. the united states would try negotiation before resorting to committing troops