Vamos analisar cada alternativa: A) "Third Conditional sentences are used to refer to unreal possibilities in the future." — Incorreto. O Third Conditional refere-se a situações irreais no passado, não no futuro. B) "Third Conditional sentences are used to refer to real possibilities in the future." — Incorreto. O Third Conditional não trata de possibilidades reais nem do futuro. C) "Third Conditional sentences are used to refer to unreal past situations." — Correto. Essa é a função do Third Conditional. D) "Third Conditional sentences are formed by the past simple in the if-clause and the past simple in the result clause." — Incorreto. Essa estrutura corresponde ao Second Conditional. E) "Third Conditional sentences are formed by the past perfect in the if-clause and would/could/might+have+past participle in the result clause." — Correto. Essa é a formação correta do Third Conditional. Portanto, as alternativas corretas são C e E. Como a questão pede a alternativa correta que contenha todos os itens verdadeiros, a resposta correta é: e) Third Conditional sentences are formed by the past perfect in the if-clause and would/could/might+have+past participle in the result clause.