An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?

Both "A is a candidate key" and "A is a primary key"

An instance of relational schema R(A, B, C) has distinct values of A i

1.	An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?
A.	A is candidate key
B.	A is not a candidate key
C.	A is a primary key
D.	Both "A is a candidate key" and "A is a primary key"
Answer» B. A is not a candidate key

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An instance of relational schema R(A, B, C) has distinct values of A including NULL values. Which one of the following is true?

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