logical deduction - Shapes and letters. What is the missing box?

_{Finally, someone has figured it out. Good job.}

Answer

I believe the answer is

1

Reasoning:

I replaced letters with numbers (A=1, B=2, C=3 and D=4) as well edges in shapes with numbers (circle = 0, line = 1, triangle = 3 and square = 4). The sum of letters and the sum of the edges matches in each row. For example the first row: B+D+B+D=2+4+2+4=12 Square+Line+Triangle+Square=4+1+3+4=12 EDIT: It's also true for columns.