Look at the following statements: (a) For any relation schema, there is a dependency-preserving decomposition into 3NF. (b) For any relation schema, there is not a dependency-preserving decomposition into 3NF. (c) For any relation schema, there is a dependency-preserving decomposition into BCNF. (d) For some relation schema, there is not a dependency-preserving decomposition into BCNF.