How can you stop young people finding bad material on the Internet?

How can you stop young people finding bad material on the Internet?
My teacher threw this question to me. And it's part of my oral test. But i don't know how to answer it. "/

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).