One of the most successful commercial products ever launched is said to have come about as the result of a mistake. In 1896, by accidental 【M1】______ adding fizzy water instead of still water to the recipe, a pharmacist called John S. Pemberton invented that has today become the most popular 【M2】______ soft drink in the world: Coca-Cola. Coke has enjoyed huge success worldwide, particularly in the past fifty years. Indeed, old Coke bottles and 'limiting edition' cans can often fetch considerable 【M3】______ sums from collectors, and there are even stores which deal exclusively Coke products and 【M4】______ collectables. What could possibly account for the amazing success of Coca-Cola? How has this combination of carbonated water, sugar, acid and flavourings come to symbolize the American way of a life for 【M5】______ most of the world? After all, even the manufacturers could hardly describe Coke as a healthy product yet it contains relatively high 【M6】______ amounts of sugar and phosphoric acid, both of that are known to damage teeth. 【M7】______ One explanation may be found in the name. The original recipe included a flavouring from the coca plant and probably included small amounts of cocaine, but since the early part of the last century all traces of cocaine have removed. 【M8】______ However, Coke also includes a flavouring from the cola tree; cola extract contains caffeine, which is a stimulant, and the Coca-Cola company adds extra caffeine for good measure. While caffeine is not thought to be an addictive substance by itself, there is considerable evidence 【M9】______ that in a period of time the consumption of 【M10】______ caffeine has to be increased in order for its stimulating effect to be maintained, and so sales of Coke perhaps benefit as a result. 【M1】