A.I. Explanation:

Option 1: "A return to the use of popular music in classical compositions"

Explanation: The text states that Philip Glass revived the practice of using elements of popular music in classical composition, which had been dormant in the U.S. during the 1960s. This directly supports the idea of a return to this practice, aligning with the main theme of the text.

Option 2: "An attempt to elevate rock music to an artistic status more closely approximating that of classical music"

Explanation: While Glass incorporates elements of rock music, the text emphasizes that his music is not merely an elevation of rock to classical status. Instead, it highlights that his compositions are distinctively his own and not just a version of popular music, making this option misleading.

Option 3: "A long-standing tendency to incorporate elements from two apparently disparate musical styles"

Explanation: The text mentions that Glass's music has shared certain harmonies and rhythms with rock music from its early days, indicating a long-standing tendency to blend these two styles. This aligns with the correct interpretation of the text's main idea.

Option 4: "Glass's classical music is a type of courtsey."

Explanation: This option is incorrect as it misinterprets the text. There is no mention of 'courtesy' in relation to Glass's music; rather, the text focuses on the distinctiveness and high art nature of his compositions, making this option irrelevant.

Option 5: "David Bowie and Brian Eno are common musicians."

Explanation: The text does not describe Bowie and Eno as 'common' musicians. Instead, it highlights their influence on Glass's symphonies, but does not imply that they are common in any sense. This option is therefore inaccurate.