ER diagrams and functional dependency

Question

Let R represents an one to many relationship between entities E1 and E2 and the set A, B attributes represent the key of R (A is key for E1 and B is key for E2) then which of the following statements is correct?

1.  The FD, A→B will only holds
2.   The FD, B→A will only holds
3.   (a) and (b) hold together
4.   Neither (a) nor (b) holds

Comments

why so?? any specific reason as to why cardinality of E2 is 1 if E1:E2=1:n  ?

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cardinality of entity means max numbers of relationship it can participate.. 

if E1 : E2 is 1 : N i.e. one value in E1 is associated with one or more values is E2

the reason is hidden in your statement....one value of E1 is associated with one or more value of E2 i.e cardinality(E1)=n,

similiarly one value of E2 is associated with only one value of E1 i.e cardinality(E2)=1

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Got it. Thank you!