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2 Answers

3 votes
3 votes

I think  3rd option is wrong because 

professor(t[ID]=t[id] ^ t[salary]>10000) , here t[ID]=t[id] ^ t[salary]>10000 is acting on argument which is is not ranging over entire table professor 

BUT, in tuple crelation calculas says that we have to make variable t which is to be range over entire table 

                                                                       like, professor(t)^condition applied on t

                                                                                          or

                                                                                t$\epsilon$professor ^ condition on t

so option 2 is carrect which satisfy the formate of TRC

3 votes
3 votes
Third option is wrong because it only project "Id". Question asks to project all fields (ID,NAME,DEPTNAME,SALARY).

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