At the grocery store last week, small boxes of facial tissue were priced at 4 boxes for \$ 5. This week they are on sale at 5 boxes for \$ 4. The percent decrease in the price per box during the sale was closest to
Answer Choices
A. 30 \%
B. 35 \%
C. 40 \%
D. 45 \%
E. 65 \%