Correct Answer: (a) an octave
Solution:Petrarchan sonnet, also known as the Italian sonnet, is a sonnet named after the Italian poet Francesco Petrarch. It has two parts: first an octave, which has eight lines (ABBA ABBA). Second part of the sonnet is called sestet, has six lines (CDE CDE or CDCDCD).
Hence, right option will be (a).