Which of the following statements regarding characteristics of contour lines is INCORRECT?
- AContour lines close to one another indicate a steep slope.
- BContour lines of different elevations cannot intersect.Correct
- CContour lines of different elevations can unite to form one line only in the case of vertical cliff.
- DContour lines of different elevations cannot cross each other.
Solution
Concept
Contours of different elevations do not meet, except at a vertical cliff (they unite) or an overhanging cliff (they intersect or cross).
Step-by-step solution
1. Check A: contours close together mean a steep slope. Correct. 2. Check C: at a vertical cliff, contours of different elevations merge into one line. Correct. 3. Check B: it says contours of different elevations 'cannot intersect'. At an overhanging cliff or cave they do intersect, so this absolute statement is not fully true. 4. Check D: 'cannot cross' is the usual general rule, but it also has the same overhanging cliff exception. 5. B and D say nearly the same thing. B is taken as the intended incorrect statement.
Explanation
Contour lines of different elevations normally do not meet. They unite only at a vertical cliff and intersect only at an overhanging cliff or cave. So the absolute claim that they 'cannot intersect' is incorrect.
Why the other options are wrong
A: True, close contours mean a steep slope. C: True, contours unite at a vertical cliff. D: Given as the general rule that contours do not cross. It has the same exception as B, so it is ambiguous.
Shortcut
Vertical cliff = contours unite. Overhanging cliff = contours intersect.
Common mistake
Thinking contours can never meet, and forgetting the vertical cliff and overhanging cliff exceptions.
Correct answer: B) Contour lines of different elevations cannot intersect.