Help on this question please! I don't think the first one is the answer but I couldn't unselect so I just let the cursor pick a random one

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.

What is the approximate area of a circle with a radius of 15 feet

In general which explains why communist revolutions did not happen