Write a short summary for this text: china has tightened regulations prohibiting the sale of alcohol to minors in what appeared to be a step toward establishing a legal drinking age , state press reported thursday .

Summary:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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china tightens controls on sale of alcohol to minors