Question

Contours of different elevations may cross each other only in the case of ____

• A. An overhanging cliff
• B. A vertical cliff
• C. A saddle
• D. An inclined plane

Hint:

Contour line rules: \[ \boxed{ \begin{aligned} \text{Never intersect} &\rightarrow \text{Normal ground}\\ \text{Coincide} &\rightarrow \text{Vertical cliff}\\ \text{Cross} &\rightarrow \text{Overhanging cliff} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: Recall the basic rule for contours.
A contour joins points of one fixed elevation, and since any single point on the ground can only have one elevation, contours of different values normally never touch or cross each other.
Step 2: Ask when that basic rule could break down.
The rule assumes each plan position corresponds to a single elevation, but that assumption fails wherever the ground surface overhangs itself, since then one plan position actually corresponds to two different elevations, one above the other.
Step 3: Identify that physical situation.
This exact condition happens only at an overhanging cliff, where rock projects out above a lower surface, so this is the one case where contours of different elevations are drawn crossing each other.
\[ \boxed{\text{An overhanging cliff}} \]