Which best shows that the author's purpose is to explain how to tune a guitar?
A. The author claims that the string at the top is thickest.
B. The author outlines the steps that readers should take to tune a guitar.
C. The author provides a detailed description of the different types of guitars.
D. The author discusses the history of the guitar and its influence on music.
Answer: B. The author outlines the steps that readers should take to tune a guitar.