Choose all of the correct answers for each of the following: [1] The number of superkeys of a relation R(A, B, C, D) with keys {A} and {B, C} is
1-2..
2- 10..
3- 12..
4- All of the above..
5- None of the above..
[2] The relations of two subentities of the same entity set have
1- The same keys..
2- The same attributes..
3- The same functional dependencies..
4- The same natural joins with their super entity set..
5- All of the above..
6- None of the above..
[3] A relation R
1- Is in BCNF if R is in 3NF..
2- Is in 3NF if R is in BCNF..
3- May be in BCNF but not in 3NF..
4- May be in 3NF but not in BCNF..
5- May be neither in BCNF nor in 3NF..
6- All of the above..
7- None of the above..
[4] The natural join of relations R and S may be expressed as
1- (oc(R x S))..
2- 0ca_ (R x S))..
3- Neither "1" nor "2"..
4- Either "1" or "2"..
[5] A tuple constraint that references an attribute R. A to attribute S. B is checked
1- When changes in R are made..
2- When changes in R. A are made..
3- When changes in S are made..
4- When changes in S. B are made..
5- Any of the above..
6- None of the above..