单选题 Why does cream go bad faster than butter? Some researchers think they find the answer,and it comes down to the structure of the food, not its chemical eomposition--a finding that couldhelp rid some processed foods of chemical preservatives.
Cream and butter contain pretty much the same substances, so why cream should sour muchfaster has been a mystery. Both are emulsions--tiny globules(小球)of one liquid evenly distributedthroughout another. "The difference lies in what's in the globules and what's in the surroundingliquid", says Brocklehurst, who led the investigation. In cream, fatty globules drift about in asea of water. In butter, globules of a watery solution are locked away in a sea of fat. The bacteriawhich make the food go bad prefer to live in the watery regions of the mixture. "This means that incream, the bacteria are free to grow throughout the mixture", he says.
When the situation is reversed, the bacteria are locked away in compartments (密封的)buried deep in the sea of fat. Trapped in this way, individual colonies cannot spread and rapidlyrun out of nutrients. They also slowly poison themselves with their waste products. "In butter, youget a self-limiting system which stops the bacteria growing", says Brocklehurst. The researchersare already working with food companies keen to see if their products can be made resistant tobacterial attack through alterations to the food' s structure. Brocklehurst believes it will be possibleto make the emulsions used in salad cream, for instance, more like that in butter. The key will beto do this while keeping the salad cream liquid and not turning it into a solid lump.

单选题 The significance of Brocklehurst' s research is that______

A. it suggested a way to keep some foods fresh without preservatives
B. it discovered tiny globules in both cream and butter
C. it revealed the secret of how bacteria multiply in cream and butter
D. it found that cream and butter share the same chemical composition

【正确答案】 A

【答案解析】[解析] 依据是文章第1段第3行的内容。

单选题 According to the researchers, cream sours faster than butter because bacteria______

A. are more evenly distributed in cream
B. multiply more easily in cream than in butter
C. live on less fat in cream than in butter
D. produce less waste in cream than in butter

【正确答案】 B

【答案解析】[解析] 依据是文章第3段相关内容。

单选题 According to Brocklehurst, we can keep cream fresh by______

A. removing its fat
B. killing the bacteria
C. reducing its water content
D. altering its structure

【正确答案】 D

【答案解析】[解析] 依据是文章最后一段相关内容。

单选题 The word "colonies" ( Line 2, Para.3) refers to______

A. tiny globules
B. watery regions
C. bacteria communities
D. little compartments

【正确答案】 C

【答案解析】[解析] 根据该词出现的语境，并根据上下文判断，应该是“菌落”的意思。

单选题 Commercial application of the research finding will be possible if salad cream can be maderesistant to bacterial attack______

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

【正确答案】 D

【答案解析】[解析] 依据是最后一段相关内容，注意：该句中的while是时间概念，相当于in thecourse of。