Question: If we want to include attributes from two different relations, which of the following operations is needed?

Answer:

Consider a Query to find the names of all bank customers who have either an account or a loan or both. Note that the customer relation does not contain the information, since a customer does not need to have either an account or a loan at bank. To answer this query we the information in the depositor relation and in the borrower relation.

So the expression needed is

Π customer-name (borrower) U Π customer-name (depositor)