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Which of the following is allowed in the Relational Data Model? O A. Primary keys with more than one attribute. B. Attributes of different relations with the same names. For example, R(A,B,C) and S(B,D,E) is allowed. C. Relations with more than one key, i.e. collection of attributes which are a minimal superkey. OD. All of the above E. None of the above A superclass called Gin an EER schema participates in an overlapping total specialization with three subclasses, 51, 52, and 53, which of the following statements is the only one that is true about G, S1, S2, S3, and their relationship? OA. A single instance of G can be related to an instance of S1, an instance of 52, and an instance of 53. OB. Some instances of G will not be related to any instance of S1 or 52 or 53- OC. An instance of S3 may not be related to any instance of G. OD. All of the above E. None of the above