Please help with this

What event brought the us into wwii? what conflicts happened after the us entered the war? i know the first part of this question, i need with the second part.

Which statement describes an important outcome of the congress of vienna? a. napoleon launched his final european military campaigns. b. european states had their borders clearly defined. c. jewish people were given equal right in germanic states d. the slave trade became increasingly important to european economies.

What is the difference between an independent and a dependent variable?