When an entity is called "weak"?
(a) When it is used to represent weak objects, such as patients, elders
(b) When all of its attributes can not identify itself
(c) When It always needs support from other entity
(d) When It is not really necessary in the ERD
a.(a) and (b) are correct
b.(b) and (c) are correct
c.(c) and (d) are correct
d.(d) and (a) are correct
Answer: B