VERY IMPORTANT OBSERVATION

If you want a balanced answer sheet, on your original exam:

1) Always use balanced (and random) answer keys on your original exam
(1c 2a 3e 4b etc), ie,

2) Never use something like this : (1a 2a 3a 4a etc)

This procedure helps random process.

A few words:
if you put unbalanced ans-sheet exam, you will get unbalanced ans-sheet exams.