If a walkway rises $2.5 \mathrm{ft}$ for every $10 \mathrm{ft}$ on the horizontal, which of the following express its slope (or grade)? (There are several correct choices.)
A. 25
B. 4
C. $\frac{2.5}{10}$
D. $25 \%$
E. $\frac{1}{4} \quad$
F. $\frac{10}{2.5}$
G. $400 \%$
H. $2.5 \%$
CAN'T COPY THE FIGURE