Given the question: Write a multi-choice question for the following article: Article: This story breaks my heart every time. Just two years after the discovery of tanzanite in 1967, a Maasai tribesman knocked on the door of a gem cutter's office in Nairobi. The Maasai had brought along an enormous block of tanzanite and he was looking to sell. His asking price? Fifty dollars. But the gem cutter assumed that a stone so large could only be glass and refused. It turned out that the gem was genuine and could have been worth close to $3,000,000! The gem cutter missed his chance to hit the jeweler's jackpot and make history. Would you have made the same mistake then? Will you make it today? In the decades since its discovery, tanzanite has become one of the world's most precious gemstones. Found in only one remote place on the Earth (in Tanzania's Merelani Hills), the precious purple stone is 1,000 times rarer than diamonds. Luxury retailers have been warning that supplies of tanzanite will not last forever. And in this case, they're right. Once the last purple gem is pulled from the Earth, that's it. No more tanzanite. Most believe that we only have a few years' supply left, which is why it's so amazing for us to offer this incredible price break. Our 2-carat Tanzanite Ring is a real bargain! This is a ring designed to impress and it does not disappoint. Now is the point where opportunity knocks, much like a Maasai tribesman on your office door. If you open that door today, you can own this excellent ring for less than $100. If you wait? We can't say for sure. Because when it comes to Africa's most prized purple stone, only one thing is certain: _ . Call now to take advantage of this limited offer. 1-888 201-7112
The answer is:
Question: The story at the beginning is mainly used to show that _ .Options:A large tanzanite is rareB tanzanite is of great valueC gem cutters might make mistakesD the price of tanzanite was once quite lowAnswer:B