The options seem a bit mis-formatted but here is the way p is computed:
the decrease is 2000-1600
and it is relative to: 2000 (2003 attendance)
so [tex]p=100 \frac{2000-1600}{2000} = 100 \frac{400}{2000}[/tex]
and so that aligns with your Option A. Options B, C, D look incorrect for sure.