In spanish when we refer to speak some language, we use the verb "saber" which in English is know. Option b is no correct because it belongs to prural form and the sentences is talking about Daniel (e.g. he).
Read carefully and choose the option with the correctly written sentence. a mis sobrinas les gusta jugar la guitarra. a mis sobrinas le gustan tocar la guitarra. a mis sobrinas les gusta tocar la guitarra. a mis sobrinas le gustan jugar la guitarra.