Which of the following statements is NOT true about knowledge representation? A. A ‘Frame’ is an artificial intelligence data structure used to divide knowledge into substructures by representing "stereotyped situations". B. By using a ‘Frame’ as a knowledge representation, it is difficult to create knowledge due to the complicated structure. C. By using a ‘Semantic Network’ as a knowledge representation, it is difficult to represent very complicated concepts or cause-and-effect relationships. D. By using a ‘Rule’ as a knowledge representation, it is suitable for the problem domain if it requires a single conclusion.