1. In a database, there are values a data element can take, and there are values it cannot take. In other words, data element values should be within correct ranges. For example, ages of employees should be between 18 and 80. Which one of the following database features ensures that? a) Security b) Data Integrity c) Data Sharing d) Concurrency Control e) Data Independence 2. Which one/ones of the following uniquely distinguishes the tuples of a relation? a) primary key b) super key c) candidate key d) alternate key e) foreign key f) a, c, and e g) a, b, c, d, and e. h) a, b, c, and d. 3. Which one(s) of the following may exist more than once for a relation? a) primary key b) super key c) candidate key d) alternate key e) foreign key f) a, b, and c g) b, c, and d h) b, c, d, and e h) a, b, c, and d. i) a, b, c, and ej) a, b, c, d, and e. 4. In the Relational Model, the primary key of a relation is selected from the a) composite keys b) super keys c) candidate keys d) alternate keys e) foreign keys