"The professor's explanation was lucid, making the complex topic easy to underst...

Questão de Inglês da banca CPCON aplicada no concurso Prefeitura de Barra de Santana PB (2024). Confira a resolução completa abaixo:

"The professor's explanation was lucid, making the complex topic easy to understand."
What sentence uses the CORRECT antonym for the word "lucid" as used in the sentence above?