Which statement is true regarding constraints?

A.
A table can have multiple primary key constraints.

B.
Informational constraints tell DB2 what rules the data conforms to, but the rules are not
enforced.

C.
Foreign key constraints are enforced on the values within the rows of a table, or between
the rows of two tables, by a unique index on a foreignkey.

D.
A table can only have one unique key constraint.