Consider the last 400 years of history, was the Columbus Exchange mostly positive or negative for Europe and for the Americas and why?

How did the united states respond when north vietnam attacked a us warship and sent troops to south vietnam in the early 1960s? a. the united states declined to assist south vietnam against the north. b. us leaders authorized south vietnam to invade north vietnam. c. the president did not sign the gulf of tonkin resolution. d. congress authorized the president to escalate the conflict.