89) Let R is a relation schema, R(A, B, C, D) and F = {A —> B, B --> C, C —> A) is the set of functional dependency. Determine the key of relation ?

91) It is desired to design an object-oriented employee record system for a company. Each employee has a name, unique id and salary. Employees belong to different categories and their salary is determined by their category. The functions geName, getId and compute Salary are required. Given the class hierarchy below, possible locations for these functions are:
(i) getId is implemented in the superclass
(ii) getId is implemented in the subclass
(iii) getName is an abstract function in the sup

92) Let r be a relation instance with schema R = (A, B, C, D). We define r1 =∏ A,B,C (r) and r2 = ∏A, D(r)
Let S = r1* r2 where * denotes natural join. Given that the decomposition of r into r1 and r2 is lossy, which one of the following is TRUE?

93) Let E1 and E2 be two entities in an E/R diagram with simple single-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. RI and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model?

94) The file organization that provides very fast access to any arbitrary record of a file is