Final answer:
To become a network administrator, pursue the CompTIA A+ certification, which provides foundational IT skills directly relevant to network administration duties.
Step-by-step explanation:
When looking to land a job as a network administrator, the most relevant certification from the options provided is CompTIA A+. This certification covers a broad range of foundational IT skills, including networking and troubleshooting, which are critical skills for any network administrator. While the CISSP is a highly regarded certification in security, the PMP in project management, and the CSM in agile project management, they are not as specifically targeted to network administration as the CompTIA A+ certification.