Bitcoin and other so-called cryptocurrencies(加密货币) have been all over the news lately.Apparently, the idea of money that's not tied to a specific bank -or a specific country - is appealing to many. But it's worth remembering that the banking system that we now all live with is just that: A modern invention. Not so long ago, money was almost always created and used locally, and bartering was common. In fact, it still is common among many online local networks, like the Buy Nothing Project.).In the past, money's makeup varied from place to place, depending on what was considered valuable there. So while some of the world's first coins were made from a naturally occurring hybrid of gold and silver called electrum(银金矿), objects other than coins have served as currency, including beads, ivory, livestock, and cowrie shells. In West Africa, bracelets of bronze or copper were used as cash, especially if the transaction was associated with the slave trade there. Throughout the colonial period, tobacco was used in lieu of coins or paper bills in Virginia, Maryland and North Carolina, even though it was used elsewhere in the colonies and extensively throughout Europe and the U.K.Today, on an island in the Pacific, a specific type of shell still serves as currency-and some people there are even hoarding(贮存) it, just like Bitcoin moguls, convinced that one day, it will make them wealthy beyond imagination.On Malaita, the most-populated island that's part of the Solomon Islands, shells are accepted at most places in exchange for goods."How much tuna(金枪鱼) you can get for your shells depends on their color and shape," Mary Bruno, a shop owner from the small town of Auki, on Malaita, told Vice. "One strip of darker shells might get you about two cans of smaller tuna, but the red ones are worth more. For the red ones, one strip might get enough tuna to feed a big family for a long time."Just like a mint that creates coins, there's only one place on the island where the shells, which are polished and strung together to form 3-foot-long ropes, are made.The strips of red, white, and black shells all come from Langa Langa Lagoon, where artificial islands were long-ago built by locals to escape from the island-dwelling cannibals. Once marooned(困住) out on their islands, locals needed a currency to use among themselves, and so the shell currency was born.Using shells for money was common throughout the Pacific islands as late as the early 1900s, but Malaita is unique in that they are still used today. And just like cryptocurrencies, there are those who think the islanders are smart to invest in this type of money, which is reported to have risen in value over the last three decades. It might seem strange to hoard a bunch of processed, strung-together shells, but what is a pile of dollars? Just a specially printed piece of paper and hemp that we've assigned value to—and probably less durable over time than those shells.According to the passage which of the following is TRUE?A. Money was created and was widely used in the world.B. Tobacco was used as coins or paper bills in American in the past.C. The ingredients of world's first coins may be the combination of gold and silver.D. Using shells for money has been out of date in the world.