A radio amateur may install an amateur station for another person under what condition?

The correct answer is based on the regulations governing amateur radio operations, which stipulate that an amateur station may only be operated by individuals who hold a valid Amateur Radio Operator Certificate. This ensures that the operator is knowledgeable about the rules, technical standards, and safety protocols necessary for responsible radio operation. Being certified not only demonstrates that the individual has passed the necessary examinations, thus acquiring essential knowledge of the relevant regulations and procedures, but it also aligns with the requirement to maintain accountability and adherence to the law.

While the other options present scenarios that might seem relevant, they do not meet the fundamental requirement of operator qualification. Temporary installations or supervised operations do not negate the need for the individual to be properly licensed. The focus on a valid Amateur Radio Operator Certificate underscores the importance of proficiency and legal compliance in amateur radio practice.