Which of the following restrictions do you think should apply to the use of the terms entity subtype and entity supertype? (a) an entity subtype must have the same identifier as its supertype; (b) an...

Which of the following restrictions do you think should apply to the use of the terms entity subtype and entity supertype?

(a) an entity subtype must have the same identifier as its supertype;

(b) an entity subtype must have obligatory participation in its relationship with its supertype;