Magnetic terms and lines: identify the correct statements about declination and related isogonic/agonic lines.

Introduction / Context:
Converting between magnetic and true bearings requires understanding magnetic declination and the map of its spatial variation. Standard terms include declination, isogonic lines, and agonic lines, used on navigational and topographic charts.

Given Data / Assumptions:

• Magnetic meridian differs from the true meridian by declination.
• Declination varies with place and time.
• Charts show contours of equal declination.

Concept / Approach:

Magnetic declination is the angle between magnetic and true meridians (east or west). Lines of equal declination are isogonic lines; the special case where declination is zero (magnetic and true meridians coincide) defines agonic lines.

Step-by-Step Solution:

Verification / Alternative check:

Map margins and geophysical references adopt these definitions universally.

Why Other Options Are Wrong:

Each A–C is correct; thus D (“All the above”) must be selected; E is false.

Common Pitfalls:

Confusing agonic with isoclinic (equal dip); mixing grid convergence with declination.

Final Answer:

All the above.