Step 1: Understanding Moon's Formation and Composition.
The Moon's composition differs from the CI carbonaceous chondrite because it was formed under high-temperature conditions, leading to the depletion of volatile elements and the enrichment of refractory elements.
Step 2: Evaluating the Options.
- Option (A): Incorrect. The Moon is indeed depleted in volatile elements but enriched in refractory elements.
- Option (B): Correct. The Moon's mantle is depleted in volatile elements and enriched in refractory elements compared to CI chondrites.
- Option (C): Incorrect. The Moon has a lower Rb/Sr ratio compared to CI chondrites, reflecting the depletion of volatiles and the overall higher abundance of refractory elements.
- Option (D): Correct. The Moon has a lower K/U ratio than CI chondrites, which is consistent with its enrichment in refractory elements and depletion in volatile elements.
Thus, the correct answer is (B) and (D).
Final Answer:
\[
\boxed{(B), (D)}
\]