a rule that states each foreign key value must match a primary key value in the other relation is called the

Referencial Integrity Contraint

Explanation:

The referential integrity constraint states that the customer ID i.e (CustID) in the Order table must match a valid CustID in the Customer table. Most relational databases have declarative referential integrity. That is to say, when the tables are created the referential integrity constraints are set up so as to maintain the quality of information.

answer; insolated i/o uses separate memory space,and on the other hand memory mapped i/o uses memory from the main

the answer is b) 2nd

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