A map is prepared with a scale of $1: 1000$ and a contour interval of $1 \mathrm{~m}$. If the distance between two adjacent contours on the map is $10 \mathrm{~mm}$, the slope of the ground between the adjacent contours is
- $30 \%$
- $10 \%$
- $35 \%$
- $40 \%$