question about database, thank you

1 select all options that are incorrect statements about a candidate key.

a any set of attributes that is a super key and is an option as a primary key

b any set of attributes that is a super key

c any set of attributes in a relation whose values can uniquely identify tuples in that relation

d any set of attributes that is a super key and in which every attribute in the set is said to be a sufficient and necessary part of the set

which of the following statement is true?

a an association class refer to junction table

b the instances of an association class are independent of the instances of the classes involved in the association

c an association class can be attached to any binary association(1 to 1, 1 to m, m to m)

d all are true statement