Explanation: FCC regulations, specifically those governing Commercial Radio Operators (found in 47 CFR Part 13), dictate that an individual may only hold one unexpired radiotelegraph operator certificate at any given time. When a licensee qualifies for a higher grade certificate (e.g., upgrading from a Second Class to a First Class Radiotelegraph Operator Certificate), the lower grade certificate is superseded and effectively canceled. The privileges of the higher-grade certificate encompass all privileges of the lower grade, making it unnecessary and disallowed to hold both simultaneously. Therefore, the lower grade is canceled. Options A and B are incorrect because the license isn't simply allowed to expire or modified; it's replaced. Option D is incorrect as it directly contradicts the FCC rule of holding only one such certificate.