Which of the following scientific or technological breakthroughs did not occur within the first fifteen years of the 20th century?

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Albert Einstein introduced the theory of relativityWireless signals were transmitted across the Atlantic OceanThe internet was developedThe first successful airplane was inventedNone of the above

Explanation

Options A, B, and D all happened before 1915: Einstein's theory of relativity was published in the early 1900s, wireless transatlantic communication was achieved in 1901, and the Wright brothers invented the airplane in 1903. However, the internet was created much later, in the late 20th century, making option C the correct choice.