DBMS FD and MVD relation

Question

If( A->D and D->->C ) => A->-> C

Is this implication valid?

Comments

MVD are not in syllabus right??

Answer 1

No, this is not valid. Each functional dependency is MVD but not Vice Versa.
Suppose if it was as A->D and D->C then A->->C is correct as A->D and D->C implies A->C

Comments

I know it is generally false,but i am asking one particular case in question?Can you tell me why the implication is false?

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because D->->C doesn't imply that D->C, hence A->C isn't implied too in this particular case.

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For every single value of A i have one value of D and for every one value of D i have multi value of C,then i can say that for every value of A there will be multi value of C. I dont see the reason for it to be false.

If i say For every every student Id there is a unique phone number.

Id -> Phone and then i say for every phone number i have multiple email ids.Then for every student id i will definitely have multiple emails.Please correct me if i am wrong