From statement I: C is to the east of B and A is to the south of B.
Clearly, we can get the direction of A with respect to C.
Therefore, A is in the south-west direction of C.
So, the data in statement I alone is sufficient to answer the question.
From statement II: D is the west of A.
We cannot determine the direction of A with respect to C.
So, the data in statement II alone is not sufficient to answer the question.
Hence, the data in statement I alone are sufficient to answer the question, while the data in statement II alone are not sufficient to answer the question.