When selecting an identifier, one should: A) use intelligent ...

[folubunmi]

When selecting an identifier, one should:
 
  A) use intelligent keys.
  B) use large composite keys instead of single-attribute surrogate keys.
  C) choose a candidate key that will not change its value over the life of each instance of the entity type.
  D) choose a candidate key such that for each instance of the entity, the attribute is guaranteed to have valid values or is null.
  E) choose a candidate key that allows for duplicate values.

Question 2

On a data-flow diagram, you may:
 
  A) repeat data stores and processes.
  B) repeat sources/sinks and processes.
  C) only repeat processes.
  D) repeat relationships.
  E) repeat both data stores and sources/sinks.

[mtmmmmmk]

Answer to Question 1

C
Explanation: C) An identifier uniquely identifies an entity instance. Because of this role, it cannot be null.
CL

Answer to Question 2

E
Explanation: E) While you may repeat data stores, sinks and sources, there is no reason to have two processes with the same name.
CL