Final answer:
None of the provided statements about vodka production are completely correct; vodka can be produced in any country, a variety of ingredients can be used, and charcoal filtering is a common practice but not a legal requirement.
Step-by-step explanation:
The student has inquired about the legality and production parameters of vodka. To answer the question directly: none of the given statements are entirely correct. Vodka can indeed be produced in any country around the world, not just within the EU and the United States; this debunks statements 1 and 2. When it comes to permissible grains, there are no legal stipulations limiting vodka production to just wheat, rye, barley, and corn, as many other sources like potatoes and grapes are also used; this negates statement 3. Lastly, statement 4 suggests that charcoal filtering is a legal necessity in vodka production, which is not a universal legal requirement, although it is a common practice. Therefore, the true statement is that vodka can be produced in any country.