Three grandsons of the emperor Charlemagne became rulers became rulers of territories that would include all of the following modern day states except

Charlemagne was the first ruler of the Holy Roman Empire, which included today's Germany, Italy, and Switzerland. Additionally, Charlemagne was a ruler of the Franks (today's France)

So the Grandsons were rulers of Germany, Italy, France, but for example not ot England: so if England is among the options, this is the correct answer.