You have been asked to examine a database to evaluate referential integrity. Which of the following should you review? A. Field B. Aggregation C. Composite key D. Foreign key Solution D. The foreign key because it refers to an attribute in one table whose value matches the primary key in another table. Answer A is incorrect because the field refers to the smallest unit of data within a database. Answer B is incorrect because aggregation refers to the process of combining several low-sensitivity items, with the result that these items produce a higher-sensitivity data item. Answer C is incorrect because a composite key is two or more columns that are together designated as the computer’s primary key..

1. _______ are any substances that when introduced into the body, stimulate the immune system to
produce antibodies. Examples of these substances are toxins bacteria foreign blood cells, and the
cells of transplanted organs.
Solution
Antigens are any substances that when introduced into the body stimulate the immune systems to
produce anti bodies.