The correct answer is A) Parallels, except the equator, appear as curved lines. On a gnomonic chart, which is a projection centered on a specific point, parallels (lines of latitude) appear as curved lines, except for the equator which appears as a straight line. This is because the projection preserves direction, but distorts distance and shape. The other options are incorrect: B) Meridians (lines of longitude) appear as straight lines converging toward the nearer pole on a gnomonic chart. C) A rhumb line, which maintains a constant bearing, appears as a curved line on a gnomonic chart. D) Distance is not measured at the mid-latitude of the track line on a gnomonic chart, as this projection does not preserve scale.