Select box 4 Tables

Hello and sry for my english.

I have no idea what can i do with my problem. I hope everybody can help
me.

I have 4 Tables.

Table A
a_id

Table B
b_id
a_id
c_id

Table C
c_id
d_id

Table D
d_id

whit the table-association A 1–n B n–1 C n–1 D

In my View i have a f.select for the association A-B-C.

The Problem is that i have in the selectbox double-data and i need one
more selectbox for the association C–D in the same View. Like this

I have search for the answer but i can find a solution for my problem.

Thank you very very very much.