*Explanation: System administrators manage the upgrade and installation of new hardware and software, perform troubleshooting to address any problems with computer systems, and assess viruses and potential threats to a company's network1.
Therefore, the correct answer is D. System administrator.

Google Apps, Dropbox, and GoToMeeting are all examples of Software-as-a-Service (SaaS). SaaS is a software distribution model in which a third-party provider hosts applications and makes them available to customers over the internet. This contrasts with IaaS, which provides virtualized computing resources over the internet, and PaaS, which offers hardware and software tools over the internet.
1.Google Apps (now Google Workspace) provides productivity and collaboration tools.
2.Dropbox offers cloud storage and file synchronization services.
3.GoToMeeting is an online meeting, desktop sharing, and video conferencing software.
All three services are accessed over the internet and do not require users to manage hardware or software updates, which is characteristic of the SaaS model.
References: The information is verified by multiple sources that discuss cloud service models, including articles that specifically categorize Google Workspace, Dropbox, and GoToMeeting as SaaS12. Additionally, Google's support documentation for GoToMeeting integration with Google Workspace further supports this classification3.