6. What does the sentence “It’s his way to turn the sky form gray to blue again.” mean?
(A) Zou wants to paint a gray picture and make it blue.
(B) Zou is not happy with his photos, but he believes the sky will become blue again.
(C) Zou doesn’t find the way to take pictures of the bright blue sky.
(D) Zou is trying hard to make a difference in air pollution by taking photos of the sky.