Read the following passage and mark the correct answer to each of the questions.

Collecting maps can be an enjoyable hobby for antiquarian booksellers, a captivating interest for cartographers, a lucrative vocation for astute dealers, and an inspirational part of the occupational functioning of map catalogers, archivists, and historians. Among recognized collectibles, maps are relatively rarer than stamps, but they have had their avid enthusiasts and admirers ever since copies were made by hand only for affluent, the commanding officer, and the ship captain. Whether the interest is business-related or amateur, the economic means abundant or slim, a collection needs a theme, be it associated with contemporary changes in cartographic representation or geographic knowledge, or a more accessible goal centered on a particular mapmaker, technique, or type of subject matter. Collectors should not overlook topical maps issued predominantly or exclusively after World War II, such as navigational charts, industrial compound road layouts, or aerial projections. Potential collectors ought not to disregard two superficially prosaic, yet important themes: maps of travel routes for family trips, and maps that, for aesthetic reasons, they personally find intriguing or simply attractive. In the first case, like the box with old family photos, the collection will give the travelers the opportunity to reminisce and relive the journey. In most cases, photocopies are worthy alternatives to originals. For example, historical society collections customarily include the high quality facsimiles needed to make a collection as comprehensive and practical as possible, supplementing the contributions made by well-to-do donors and benefactors. If not predisposed to wait patiently, and possibly ineffectually, for a lucky find, collectors may choose to sift through dealer stock, peruse through advertisements in local, regional, or national periodicals, and solicit the assistance of the U.S. Library of Congress and private agencies. Government and public agencies, companies, and trade associations can advise the collector about maps currently in circulation and pending sales of dated reproductions, editions, and prints. 

What is the main idea of the passage?