A、The discovery of voice recording. B、The development of guitar and popular music. C、Les Paul’s musical experience and death D、L

Guitar legend and recording industry pioneer (先驱) Les Paul died on Thursday, August 13, at a hospital in White Plains, New York, of complications from pneumonia. He was 94 years old. Known for his virtuosity (精湛技艺 ) on guitar, Paul made breakthrough discoveries that forever changed the sound of popular music.
Les Paul single-handedly changed the course of music when he developed his solid body guitar, and discovered a new way to record voices and instruments. Paul became known as the "Wizard of Waukesha," by people in his Wisconsin home town. Born Lester William Polfuss, he was self-taught on guitar, and loved to experiment with electronic equipment.
He performed country music at a local restaurant when he was 10 years old, and by age 13, had built his own broadcasting station and recording device. He played and traveled with country bands and even hosted his own radio show in Chicago.
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4.  When did Les Paul build his own broadcasting station?