FERMAT 2005 Problem 21

Four different numbers a,b,c, and d are chosen from the list -1,-2,-3,-4, and -5. The largest possible value for the expression a^b+c^d is

Answer Choices
A. \frac54
B. \frac78
C. \frac{31}{32}
D. \frac{10}{9}
E. \frac{26}{25}