第14题: [单项选择]The stone chip is thought to be the most important tool because it______. A. was one of the first tools. B. developed human capabilities. C. led to the invention of machines. D. was crucial to the development of mankind. 参考答案:D 答案解析:本题询问细节,相关语句为第二段末尾的“The stone chip …and it is the most important.Some scientists say that it was the
第22题: [多项选择]阻力血管主要指 A. 大动脉 B. 小动脉及微动脉 C. 毛细血管 D. 小静脉 E. 大静脉 参考答案:B 答案解析:[解释] 外周阻力与血液黏滞度、血管口径及长度有关。但在一般情况下,血液黏滞度与血管长度变化不大,主要是血管的口径变化对阻力的影响极为显著蠢小动脉和微动脉的平滑肌较丰富,收缩性能强,口径只要发生很小的