The correct answer is: D. Slope of a hill cannot be determined with the help of contours.
A contour line is a line on a map that connects points of equal elevation. The closer the contour lines are together, the steeper the slope. However, the slope of a hill cannot be determined with the help of contours alone. To determine the slope, you would need to know the elevation of two points on the hill and the distance between them.
Here is a brief explanation of each option:
- A. Contour interval on any map is kept constant.
This is not always true. The contour interval is the difference in elevation between two consecutive contour lines. It can be different on different maps, depending on the scale of the map and the relief of the terrain.
- B. Direct method of contouring is cheaper than indirect method.
The direct method of contouring is a method of creating a contour map by measuring the elevation of points on the ground and then connecting them with contour lines. The indirect method of contouring is a method of creating a contour map by using aerial photographs or satellite images. The direct method is usually cheaper than the indirect method, but it is also more time-consuming.
- C. Inter-visibility of points on a contour map cannot be ascertained.
This is not true. The inter-visibility of points on a contour map can be determined by using a tool called a stereoscope. A stereoscope is a device that allows you to view two images of the same scene from slightly different angles. When you view the images through the stereoscope, the scene will appear three-dimensional. You can then use the stereoscope to determine which points on the map are visible from each other.
- D. Slope of a hill cannot be determined with the help of contours.
This is the correct answer. The slope of a hill cannot be determined with the help of contours alone. To determine the slope, you would need to know the elevation of two points on the hill and the distance between them.