Graham Stookey is an 18-year-old high school student. He plays the guitar very well. He is always interested in taking(A)____ lessons, but he didn't start until he was 13 years old. He took lessons of electric guitar and the other part of music for two years. He was kind of shy. He didn't have many friends, and kids made fun of him at school. In 2007,his dad took him to John Mayer's concert. At the concert, John Mayer played the acoustic(原声的)guitar. It sounded much more beautiful than the electric guitar. A day later, he cut the hair and picked up an acoustic guitar.(B)He started writing music and learning how to sing. He loves music very much.(C)因此练习吉他真的不是一件困难的事情。He wrote a song Jonah. It is about his brother. He's hoping to write more good songs.
When did Graham Stookey begin to learn acoustic guitar?