To live in cloud-cuckoo land - Tradução em português

someone is (living) in cloud-cuckoo-land (informal)
used for saying that someone is silly if they believe that there are no problems in a situation
(Macmillan)

live in cloud-cuckoo land
to believe that things you want will happen, when really they are impossible
Anyone who thinks this project will be finished within six weeks is living in cloud-cuckoo land.
(Cambridge Idioms)

He's living in a cloud-cuckoo land. Tradução:

a) Ele é um pobre inocente que acredita em tudo.
b) Ele tá viajando na maionese.
c) Ele vive no mundo da fantasia.
d) N.D.A. Dê sua sugestão: ___________________