[单项选择]

Why does cream go bad faster than butter Some researchers think they have the answer, and it comes down to the structure of the food, not its chemical composition — a finding that could help rid some processed foods of chemical preservatives.
Cream and butter contain pretty much the same substances, so why cream should sour much faster has been a mystery. Both are emulsions — tiny globules (小球) of one liquid evenly distributed throughout another. The difference lies in what’s in the globules and what’s in the surrounding liquid, says Brocklehurst, who led the investigation.
In cream, fatty globules drift about in a sea of water. In butter, globules of a watery solution are locked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the mixture. "This means that in cream, the bacteria are free to grow throughout the mixture," he says.
When the situation is reversed, the bact
A. by varying its chemical composition
B. by turning it into a solid lump
C. while keeping its structure unchanged
D. while retaining its liquid form

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