What group did palmer believe posed the greatest threat to the united states?

Communists

Explanation:

Attorney General A. Mitchell Palmer is well-known for the events known as the "Palmer Raids." These were a series of violent and abusive raids that were intended to target leftists radicals and anarchists in 1919 and 1920. These took place during the period known as the First Red Scare and mostly affected Italian and Eastern European immigrants.

i honesty don't know, good luck tho dawg

silk

indigo  

rice

all the other answers are wrong