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Que. Consider a relational table with a single record for each registered student with the following attributes.

1. Registration_Num: Unique registration number
of each registered student
2. UID: Unique identity number, unique at the
national level for each citizen
3. BankAccount_Num: Unique account number at
the bank. A student can have multiple accounts
or join accounts. This attribute stores the
primary account number.
4. Name: Name of the student
5. Hostel_Room: Room number of the hostel

Which one of the following option is INCORRECT?
a. BankAccount_Num is candidate key
b. Registration_Num can be a primary key
c. UID is candidate key if all students are from the same country
d. If S is a superkey such that S∩UID is NULL then S∪UID is also a superkey
Answer:BankAccount_Num is candidate key
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