If you want to continue to use the Madrid trademark after the expiration of its validity, you should renew it. The Madrid Agreement and the Madrid Protocol stipulate that the validity period of an internationally registered trademark is 1 years. Six months before the expiration of the validity period, the International Bureau will informally notify the trademark registrant about the renewal, including the expiration date of the validity period. If the registrant fails to apply for renewal before the expiration of the validity period, the International Bureau will grant a six-month extension. If no application for renewal is made within the grace period, the International Bureau will cancel the international registration. If an application is made within the above-mentioned time limit, the validity of the international registration of a trademark can be extended for 1 years. Therefore, the correct answer to this question is option C.