Holocaust denial is illegal where?

a. The United States

b. Canada and the European Union

c. The United States, Canada, and the European Union

d. Canada and the United States

I don't see any correct answers in the list provided.

Rule out the United States, where proponents of the 1st Amendment and free speech have held that Holocaust denial can't be made a crime. Only if hate speech escalates to the level of a hate crime in the US, inciting or causing direct harm to others, is it prosecuted as illegal.

Canada is similar. There have been cases brought in Canada against Holocaust deniers as a form of hate speech/hate crime, but the Canadian Supreme Court has acquitted persons accused in that way.

So from the listed options, really only in countries of the European Union will you find laws criminalizing Holocaust denial. And it tends to be more in individual countries within the EU. As a whole, the EU has not fully implemented laws specifically against Holocaust denial, although it does give member nations the option of imposing up to three years jail time for persons "denying or grossly trivialising crimes of genocide, crimes against humanity and war crimes."