Which only vegetable cannot be sold frozen or canned processed?

This is a bit of a trick question! There is no vegetable that *cannot* be sold frozen or canned.

While some vegetables freeze or can better than others, technology and processing techniques have advanced to the point where nearly any vegetable can be preserved in these ways.

Perhaps you're thinking of a specific vegetable that's rarely sold frozen or canned, like fresh herbs. They tend to lose flavor and texture when processed, so they are often preferred fresh.