To determine the correct sentence between the given options, it's important to understand the idiomatic usage of the phrases "nothing else than" and "nothing else but". The key difference lies in which phrase is commonly used in standard English and sounds correct.
Based on the analysis, the sentence in (II) is correctly constructed using standard idiomatic English, whereas the sentence in (I) is not. Therefore, the correct answer is that "is incorrect but (II) is correct".