How to interpret "a Japanese book"

(A), (B) and (D) are all possible meanings, and the context in which it is said will determine which interpretation is most likely. I think (C) is a conceivable meaning, but much less likely than any of the others. Sentence examples:
(1) After studying Japanese for three years, I was finally able to read a Japanese book. ((A) is the most likely interpretation, but "I was finally able to read a book written in Japanese" is a clearer way to say this.)
(2) Japanese books are printed on higher quality paper than books printed in the US.
((B) is the most likely interpretation.)
(3) Which Japanese book did you find most helpful when you were first learning the language? ((D) is the most likely interpretation, but "Which Japanese textbook..." is more likely to be said.)