[单项选择]债券回购业务标准券折算率的主要确定依据是( )。
A. 现券的市场价格
B. 现券的年利率
C. 回购期限
D. 资金的年收益率

{{B}}The World in a Glass: Six Drinks That Changed History{{/B}}
Tom Standage urges drinkers to savor the history of their favorite beverages along with the taste.
The author of A History of the World in 6 Glasses (Walker & Company, June 2005), Standage lauds the libations that have helped shape our world from the Stone Age to the present day.
"The important drinks are still drinks that we enjoy today," said Standage, a technology editor at the London-based magazine the Economist. "They are relics(纪念物) of different historical periods still found in our kitchens."
Take the six-pack, whose contents first fizzed at the dawn of civilization.

{{B}}Beer{{/B}}
The ancient Sumerians, who built advanced city-states in the area of present-day Iraq, began fermenting(发酵) beer from barley at least 6,000 years ago.
"When people started agriculture the first crops they produced were barl