which one of the following describes one effect of the united states entrance into world war II had on minority groups?

This looks like a trick question, so, the best way to answer it would be by elimination:

Choice B is absolutely wrong. America's entry into WWII was prompted by Japan's attack on Pearl Harbor, and caused an immediate backlash against Japanese-American citizens.

Choice C is obviously wrong, since the relationship between Americans and Mexicans had nothing to do with WWII at the time.

Choice D is also wrong since women prospered during WWII. Since all the men had gone off to fight, industries needed workers more than ever as they were a important part in producing machinery for the war. Women were the only ones to fill these roles, and played a big part in manufacturing.

So, Choice A is the most logical decision.