Final answer:
An outer join, unlike a natural join, preserves the tuples from one table that do not have a matching row in another table. Therefore, an outer join operation saves tuples that would be lost in a natural join.
Step-by-step explanation:
The question is focusing on types of SQL joins and which operation preserves the tuples that would be lost in another type of join. In relational database management systems, an outer join is used to include the rows from one table that do not have a matching key in the other table. Specifically, a left outer join preserves all tuples from the left table, providing nulls for missing matches from the right table, while a right outer join does the opposite.
A natural join, on the other hand, only returns rows where there is a match for columns with the same name in both tables. Therefore, the correct option that preserves those tuples that would be lost in a natural join is the outer join. Based on the given choices, the right answer would be (2) outer join, natural join.