Question

5. Based on this idea,he developed        the Internet (what)

基于这个想法，他开发了后来称之为互联网的东西。

Answer 1

5. what was later called这里的what弓导宾语从句，相当于the thing that ,既作主句谓语动词developed的宾语，又是后面was later called the Internet的主语。