Can anyone help with the precise answers to these questions? Thanks in advance.

a) A table created with a primary key constraint cannot have duplicate rows.

b) A foreign key constraint automatically causes the two tables involved to be JOINed into a single table for query purposes.

c) In Codds relational world (rules), can a relation have duplicate rows?

d) In a typical DBMS, like Oracle, can a table have duplicate rows when no Primary Key or Unique constraint has been defined?

d) What is a multiset?

e) Can a Primary Key be composite?

f) If your table has several candidate keys, what criteria would you use to choose the key to be designated as the Primary Key? Explain why.