Final answer:
A server can be a computer or software that provides services to other computers, software, or machines. Servers operate on different levels: the physical level (hardware), the design level (software), and the commonsense level (user perspective of services rendered).
Step-by-step explanation:
Among the choices provided, the following can be considered as servers:
- A computer that provides a service to other computers.
- A software that provides a service to other software.
- Software that provides a service to other machines.
Servers can be both hardware and software. At the physical level, the hardware aspect of a server comprises the electronic components and systems that execute instructions. At the design level, server software manages and responds to requests from client software or devices. On the commonsense level, servers perform tasks like hosting websites, managing email communication, or storing data.