In highway terrain classification by cross slope, a country with natural ground cross slope between 25% and 60% is categorized as:

Introduction / Context:
Highway geometric design begins with identifying the terrain category. The natural cross slope of the ground controls feasible gradients, curvature, earthwork, and ultimately safety and cost. Standards define threshold bands for plain, rolling, mountainous, and steep terrain to guide designers.

Given Data / Assumptions:

• Cross slope (natural ground transverse slope) of the country is between 25% and 60%.
• We use conventional Indian/International highway practice for terrain classification bands.
• No special local modifications are assumed.

Concept / Approach:
Typical bands used in design manuals are: Plain (0–10%), Rolling (>10–25%), Mountainous (>25–60%), and Steep (>60%). These bands are used to select ruling/limiting gradients, curve radii, sight distance allowances, and to estimate construction difficulty and cost.

Step-by-Step Solution:
Identify the given band: 25% to 60% cross slope.Match with standard terrain categories: this falls within the “mountainous” range.Select the matching option: Mountainous terrain.

Verification / Alternative check:
If the cross slope exceeds 60%, the terrain is classed as “steep.” If it is 10–25%, the terrain is “rolling.” Being within 25–60% clearly places it as “mountainous.”

Why Other Options Are Wrong:

• Plain (0–10%) and Rolling (10–25%) are too gentle compared to the stated 25–60%.
• Steep (>60%) is beyond the upper bound of the given range.
• Desert terrain is not a geometric category; deserts can have any cross slope.

Common Pitfalls:

• Confusing “steep” (>60%) with “mountainous” (25–60%).
• Assuming terrain depends on elevation above sea level; classification is based on cross slope.

Final Answer:
Mountainous terrain