Internet is:

The Internet is a vast and complex system that has revolutionized communication and information access worldwide. Understanding its fundamental nature is key to comprehending its impact.

• A: Single network is incorrect because the Internet is not one monolithic network; rather, it's a 'network of networks,' connecting countless smaller networks.
• C: Local network (LAN - Local Area Network) refers to a network confined to a small geographical area, like a home or office, which is a tiny component compared to the Internet's scale.
• D: Private network refers to networks restricted to authorized users, such as intranets or VPNs, whereas the Internet is largely public and globally accessible.

The correct answer is B: Global network. The Internet connects millions of private, public, academic, business, and government networks across the entire planet, enabling worldwide data exchange and communication, making it truly global in scope.