The correct answer is: 4 years.
The competency certificate of a gateman is valid for 4 years. This means that the gateman must renew their certificate every 4 years in order to continue working as a gateman. The renewal process involves taking a written exam and a practical exam. The written exam covers topics such as gate operations, security procedures, and emergency response. The practical exam involves demonstrating the ability to operate a gate and to respond to security incidents.
The 4-year validity period for the competency certificate of a gateman is designed to ensure that gatemen are up-to-date on the latest safety and security procedures. It also helps to ensure that gatemen are competent in operating gates and responding to security incidents.
The other options are incorrect because they are not the correct length of time for the validity of the competency certificate of a gateman. Option A is 10 years, which is too long. Option B is 3 years, which is too short. Option C is 9 years, which is not a valid option.