Introduction:
A contour interval is the vertical difference between contour lines on a topographic map. It represents the change in elevation between adjacent contour lines. Selecting an appropriate contour interval is crucial for accurately representing the landforms and features on a topographic map.

Given:
Scale of the topographic map: 1:25,000

Explanation:
The contour interval should be chosen based on the scale of the map and the desired level of detail. A smaller contour interval provides more detail, but it also increases the number of contour lines on the map, making it more crowded and potentially harder to read. Conversely, a larger contour interval simplifies the map but may lose important details.

To determine the suitable contour interval, we need to consider the scale of the map. A scale of 1:25,000 means that one unit of measurement on the map represents 25,000 units in real life. In this case, the units are meters.

Calculating the contour interval:
To calculate the contour interval, we need to divide the elevation range of the area being mapped by the desired number of contour lines.

Let's say we want to represent an elevation range of 200 meters on the map. Since the map scale is 1:25,000, the corresponding distance on the map would be 200 meters divided by 25,000, which is 0.008 meters or 8 millimeters.

Comparing the options:
a) 0.8 m: This option is not suitable as it is too large for the given scale. It would result in only a few contour lines, making the map lack detail.
b) 20 m: This option is also not suitable as it is too large for the given scale. It would simplify the map too much and may not accurately represent the landforms.
c) 2 m: This option is closer to the suitable contour interval. It would provide more detail on the map, but it may still result in a crowded map with many contour lines.
d) 6.25 m: This option is the most suitable contour interval for the given scale. It strikes a balance between detail and readability. It would provide enough information about the landforms without overcrowding the map.

Therefore, option 'D' (6.25 m) is the correct answer for a suitable contour interval for a topographic map drawn to a scale of 1:25,000.