Examination of a relation rel_b reveals that no candidate keys exist. Given this information, it is necessary:?

1) examination of a relation rel_b reveals that no candidate keys exist. Given this information, it is necessary:

a) re-examine the data, because someone made a mistake
b) use foreign key as a primary key
c) introduce a surrogate key to serve as a primary key
d) a and b
e) b and c
Update: 2) In a relation Rel_A(colA, colB, colC, colD, colE), the following are found to be unique: colA, colE, combination (colB, colC, colD). Are the following true or false?
a) Is colA a primary key?
b) colE is a candidate key?
c) combination (colB, colC, colD) is candidate key
2 answers 2