A contour line joins locations having the same height above the mean sea level. The following is a
contour plot of a geographical region. Contour lines are shown at 25 m intervals in this plot.
425
450
550
550
500.
— 475
The path from P to Q is best described by
Options:
(A) Up-Down-Up-Down
(B) Down-Up-Down-Up
(C) Down-Up-Down
(D) Up-Down-Up
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
37
2
38
2
39
2
40
2
41
2
42
2
43
2
44
2
45
2
46
2
47
2
48
2
49
100
to
1000
2
50
D
2
51
A
2
52
2
53
2
54
2
55
2
56
1
57
A
58
D
59
B
60
B
61
D
2
62
2
63
A
64
65
C
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2017 Q.65)**
**1. Governing Concept & Question Classification**:
- **Section**: General Aptitude (GA)
- **Question Type**: **MCQ** (2 Marks)
- **Topic**: Spatial & Topographical Map Reading (Contour Lines & Elevation Profiles)
**2. Detailed Step-by-Step Analysis**:
- A contour line connects points of equal elevation above mean sea level.
- Moving along the path from point P to point Q on the topographical contour map:
1. **From P into the valley**: The path leaves higher elevation contours (e.g., crossing from 500 m to 475 m to 450 m), moving **Down** into a low elevation valley/depression.
2. **Ascending the central ridge**: The path then ascends across rising concentric contour lines (from 450 m to 475 m, 500 m, 550 m), reaching a ridge or local summit, moving **Up**.
3. **Descending to Q**: Beyond the summit, the path descends again through lower elevation contour rings toward point Q, moving **Down**.
- Therefore, the elevation progression along the path from P to Q is sequentially characterized as **Down-Up-Down**.
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: Up-Down-Up-Down introduces an extra valley and incorrect initial climb.
- **Option (B) [INCORRECT]**: Down-Up-Down-Up introduces a final climb not present in the profile.
- **Option (C) [CORRECT]**: Down-Up-Down accurately describes the topographic elevation changes along the path from P to Q.
- **Option (D) [INCORRECT]**: Up-Down-Up reverses the topological valley-ridge profile.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **C**
- **Scoring Criteria**: +2.0 Marks (Negative marking: -0.67 marks).
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