Question: Database software performs three main types of integrity services: semantic,referential, and entity. Which of the following correctly describes one of these services?
i.A semantic integrity mechanism makes sure structural and semantic rules are enforced.
ii. A database has referential integrity if all foreign keys reference existing primary keys.
iii. Entity integrity guarantees that the tuples are uniquely identified by primary key values.
A. i,ii, iii
B. ii, iii
C. i, ii
D. i

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