According to the passage, the theory that the romances come from the same raw material as the cantares is questionable because:
Romances came into being only after the decline of the cantares.
According to the author, the cantares were in a period of “final decadence” at the time the romances were born, so it is unlikely that they came from the same raw material. Choice B is incorrect; the subject matter of romances was not the lives of everyday people. In the 2nd paragraph, the cantares are described as “usually complex,” whereas in the later part of the same paragraph, the romances are characterized as written in “simple and direct” language, making choice C also a bad choice. Since the subject matter of romances often derives from the epics, choice D is also incorrect.