Final answer:
The independent clause in the given sentence is 'While the telephone connected fifty million people within seventy-five years of its inception'.
Step-by-step explanation:
The independent clause in the given sentence is: While the telephone connected fifty million people within seventy-five years of its inception. An independent clause is a clause that can stand alone as a complete sentence, without relying on other clauses or phrases for its meaning. In this case, the independent clause expresses a complete thought and can function as a standalone sentence. The dependent clause, 'the Internet accomplished only four years', cannot stand alone as a complete sentence and relies on the independent clause for its meaning.