🔍 Key Concepts
• How depth curves (contours) are shown on U.S. nautical charts
• The standard chart symbol/line pattern for depth contours such as 10, 20, or 50 fathoms
• Differences between solid lines, broken lines, and dash‑dot patterns on charts
💭 Think About
• Look at which answer choices show a consistent repeating pattern that could represent a contour line, not an isolated object or boundary
• Think about whether a 20‑fathom curve is more like a boundary line between depths or like a special hazard/feature symbol
• Ask yourself: on real charts you've seen, do depth contours usually appear as solid, broken, or dash‑dot lines?
✅ Before You Answer
• Identify which options look like they could be used to follow a continuous line across the chart
• Eliminate any line styles you recognize as being used for different features (e.g., limits, traffic separation, or special areas, if you know them)
• Focus on the style that best matches how intermediate depth contours (not shoreline, not deep‑water limits) are normally drawn