Correct Answer is C:
Wine label information is dictated by the Treasury branch of the Federal government (used to be the "BATF"). There are very strict guidelines. If a single grape varietal name appears on the label, at least 75% of the wine must be of that varietal. Although it used to be common knowledge that Oregon state laws set this level at 90%, this was gutted in Dec-2007. At this time most familiar wines are now at 75% -- only some lesser known varietals are subject to the 90% level.
