阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
The history of Chinese currency covers more than 3,000 years. Currency of some type has been used in China since the Neolithic age (新石器时代), ____ can be traced back to between 3,000 and 4,500 years ago. Cowry shells (贝壳) are believed to have been the ____ (early) form of currency used in Central China, and were used during the Neolithic period. The use of shell money is confirmed in the Chinese writing system. The traditional ____ (character) for “goods”, “buy” and “sell”, in addition to other ____ (vary) words relating to exchange, all contain the “shell”.
Around 210 BC, the first emperor of China Qin Shi Huang (260 — 210 BC) abolished all other forms of local currency and introduced____ uniform copper coin. Although paper money ____ (invent) in China in the 9th century, the base unit of currency remained the copper coin. Copper coins were used____ the chief currency in China until the ____ (introduce) of yuan in the late 19th century.
Currently, the RMB is the official currency of China. With over 1.3 billion people ____ (use) RMB every day, it is one of the most commonly used currencies in the world. Nowadays, online payment is taking a large share in the market. Will paper money disappear one day like shells or copper coins ____ (replace) by a new way of payment? Only time can tell.
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