Which built-in account gives full access to the computer system?

Local System
Local Service
Network Service
Local User

Answer:

Local System

When you configure a service, you need to configure what account the service runs under. You can use the built-in accounts included with Windows or you can use a service account that you create locally or on the domain. The built-in accounts include:

• Local System: Highly privileged account that can access most resources on the local computer.
• NT Authority\LocalService: Has the same privileges of the local Users group on the computer. When it accesses Network resources, it uses no credentials and a null session.
• NT Authority\NetworkService: Has the same level of access as the Users group on the local computer. When it accesses network resources, it does so under the context of the local computer account.