Here's the re-arranged list, grouping sentences by their linking words/structures: "If" Clauses (Conditional Type 1, 2, and 3): (a) If we invest in girls' education, sub will/would be happy (e) If you do not work hard, (c) If we follow the rules of health, (c) If I had seen you, (d) If I had known his mobile number, (a) I am looking for Rathan. If I had seen him, (b) Had I the wings of a dove, (c) If I had the wings of a bird, "Unless" Clauses: (a) Unless you study attentively, (b) Unless you study attentively, "Lest" Clauses: (e) We must look before we leap lest (e) We work seriously lest sub should  fail (d) Take your umbrella lest (e) Take your umbrella lest "As if" Clauses: (b) Shila seemed upset. She talked as if (d) We love and help one another as if (b) He pretended as if "Provided that" Clauses: (e) Work hard provided that ...