Limiting the number of running services to only those that are essential for the server's operation significantly reduces the available entry points for an attacker, thus minimizing the attack surface. Unnecessary services can introduce vulnerabilities or become potential targets. Other options, like applying security patches or conducting a vulnerability scan, are important for maintaining security but do not directly minimize the attack surface. The use of strong encryption is essential for protecting the confidentiality of data in transit, but it does not impact the number of attack vectors.