Which four routes does the textbook name for identifying an ‘illah?

Qiyas: Definition, Authority, Five Conditions, Effective Cause and Types

• Qur’an, Sunnah, analogy and mere lexical usage
• Qur’an, single reports, custom and personal opinion
• Qur’an, Sunnah, ijma‘, and ijtihad
• Sunnah, lexicon, interests and social agreement