why is the below statement regrading weak entity correct ?

Question

Weak entity set avoids the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity..

plz clarify this........

Answer 1

clearification of above statement is in two ways

(a) weak entity is totally participated in strong entity i.e. each element of weak entity is must have some element in strong entity

but weak entity have not its own primary key it is identified by primary key of strong entity

(b) suppose if we duplicate the weak entity set then we have to duplicate the primary key as we know that primary key must contain unique value which is not possible so there will be contradiction here