taxonomy (need to assign one vocabulary terms to another vocabulary terms)

Hi,

I have created 2 vocabularies by using taxonomy.I can assign these vocabularies to content types.But now i have a requirement like,One vocabulary terms need to be displayed as select menu another create vocabulary term page.

In detail like the following,
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Vocabulary A have 3 terms a1,a2,a3
Vocabulary B is there.
Now i have to create terms for vocabulary B.
In Create terms page a1,a2,a3 need to display in a select menu.

That is my requirement.

Please help me.
Thanks inadvance.

With Regards
Chandra Sekhar Y