Concept:A Petrarchan sonnet is built from two unequal parts: an eight-line opening section and a six-line closing section.Explanation:A Petrarchan sonnet contains 14 lines in total.The first 8 lines are called the octave.The last 6 lines are called the sestet.Because 8 lines are more than 6 lines, the major part of the sonnet is the octave.The octave usually introduces the main idea or problem, while the sestet gives a response or resolution.Answer:D. octave