听力原文： （20[D])Any mistake made in the printing of a stamp raises its value to stamp col

听力原文： (20[D])Any mistake made in the printing of a stamp raises its value to stamp collectors. A mistake on one cheap postage stamp has made the stamp worth a million and a half times its original value.

The mistake was made more than a hundred years ago in the British colony of Mauritius, a small island in the Indian Ocean. (18[A])In 1847 an order for stamps was sent to a London primer — Mauritius was to become the fourth country in the world to issue stamps.

Before the order was filled and delivered, a ball was planned at Mauritius Government House, and stamps were needed to send out the invitations. A local printer was instructed to copy the design for the stamps. (19[B])He wrote by chance the words "Post Office" instead of "Post Paid" on the several hundred stamps that he printed.

Today there are only 26 of these wrongly printed stamps left — fourteen One Penny Orange-Reds and twelve Two Penny Blues. Because of the Two Penny Blue's rareness and age, collectors have paid as much as $16,800 for it.

In 1847 most countries of the world were ______.

A．not yet using postage stamps

B．collecting valuable stamps

C．buying stamps from Mauritius

D．printing their own stamps