AP Form Codes?

<p>Does anyone know anything about AP MCQ Form Codes?
It seems that there are form D, E, O usually in MCQ but we've seen that there were only form O in last yr's biology.
Is there any rule for determining the form code?
Thnx in advance</p>

<p>It’s determined by the College Board. Some exams have multiple forms, some don’t. Only they know why some tests have multiple forms. There’s different curves for each form, though.</p>