The choice of contour interval depends on several fundamental surveying considerations: (A) Time and expense available for field surveying and office plotting, where smaller intervals demand substantially greater resources; (B) Purpose and extent of survey, where detailed engineering earthwork calculations require small intervals while regional reconnaissance permits larger intervals; and (C) Scale of plan and nature of the country, where flat country requires small intervals and steep terrain requires larger intervals. Option analysis: (A) Contour characteristics (D) are geometric features of lines, not deciding criteria for selecting interval. (B) (A), (B) and (C) only correctly enumerates all three primary controlling factors. (C) Includes interpolation (E) which is an office drafting technique. (D) Omits survey purpose (B).