Which of the following occurred first ? A. Albert Einstein propounded the General Theory of Relativity B. Max Planck unveiled the Quantum Theory C. Guglielmo Marconi sent out the first wireless signals D. Wright Brothers successfully flew an aircraft

The correct answer is: D. Wright Brothers successfully flew an aircraft.

• Albert Einstein propounded the General Theory of Relativity in 1915.
• Max Planck unveiled the Quantum Theory in 1900.
• Guglielmo Marconi sent out the first wireless signals in 1895.
• The Wright Brothers successfully flew an aircraft in 1903.

The Wright Brothers were the first to achieve powered, sustained, and controlled human flight. On December 17, 1903, Orville Wright made the first successful human flight at Kitty Hawk, North Carolina. His brother Wilbur flew four more times that day, with the longest flight lasting 59 seconds and covering 852 feet.

The Wright Brothers’ achievement was a major breakthrough in aviation and paved the way for the development of modern airplanes.