Which of the following statements is correct concerning diesel engine cooling water systems?（）
A. Each engine must have its own engine driven cooling water pump capable of providing cooling for all ranges of operation
B. propulsion engines with bores exceeding 200 mm are to be fitted with a means to display the cooling water temperature of each cylinder
C. At least two independent sea suctions are to be provided for supplying water to the engine jackets or to the heat exchangers
D. Suitable strain are to be fitted between the circulating pumps and heat exchangers when sea water is used for direct cooling
孕酮是维持怀孕所必需的激素之一，以下有关孕酮的论述哪个是错误的（）
A. 孕酮可以抑制子宫的自发性活动，降低子宫肌层的兴奋作用，可促使胎盘发育，维持正常妊娠
B. 在临床上孕酮可用于防止因内源性孕激素不足引起的习惯性流产
C. 少量孕酮与雌激素有协同作用，可促进发情表现
D. 孕酮唯一来源是卵巢中的黄体细胞所分泌
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