あ、解決しました・・・。
(define (test s)
(apply append
(map
(lambda (x)
(apply append
(map
(lambda (y)
(map (lambda(z) (list x y z))
(caddr s)))
(cadr s))))
(car s))))

(test '((a b c) (d e f) (g h i)))
=>((a d g) (a d h) (a d i)
(a e g) (a e h) (a e i)
(a f g) (a f h) (a f i)
(b d　g) (b d h) (b d i)
(b e g) (b e h) (b e i)
(b f g) (b f h) (b f i)
(c d g) (c d　h) (c d i)
(c e g) (c e h) (c e i)
(c f g) (c f h) (c f i))