参考答案

正确答案：C
此题为细节题。从文中最后一段最后一句Because of the Two Penny Blue's rareness and age；collectors have paid as much as $16，800 for it可知，被高价收藏的是Two Penny Blue，原因是这种邮票非常稀少，总共才只有12张，故D为正确答案。