单项选择题
A.not yet using postage stamps B.collecting valuable stamps C.buying stamps from Neuritis D.printing their own stamps
A.the One Penny Orange-Red B.a correctly printed'1847 stamp C.the Two Penny Blue D.both A and C
A.The "Post Paid" Error B.The Two Penny Blue C.A Rare Stamp D.How Mauritius Became Famous