GRE考试

【单选题】Many microorganisms survive such environmental stresses as heat, cold and desiccation not by rapid rates of mitosis, but by producing specialized cells designed to persist in a dormant state in hostile environments. Most fungi, for Line example, yield single-celled spores, which, through wind distribution, can survive for long periods of time before germinating and sprouting fungal filaments of their own. Other types of bacteria produce a special type of spore called an endospore, capable of withstanding such extremes as boiling and freezing temperatures, and even ultraviolet radiation.　　Though research results remain tentative, several factors may protect endospores from environmental stress: they have a low water content, unusual proteins and a tough spore coat absent in mature bacterial cells. When garden fruits and vegetables, which may contain botulism endospores, are preserved by canning at boiling temperatures, we know that these spores survive the heat and sprout in the food, and as a result, the bacteria generate the botulism toxin that can lead to food poisoning―proof of their magnificent resilience. The passage mentions all of the following as environmental stresses that can be survived by microorganisms that practice cellular dormancyEXCEPT________.
A、Low temperatures
B．Ultraviolet radiation
C．Acidic environments
D．High temperatures
E．Drying processes

网考网参考答案：C
网考网解析：
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