关于红细胞的叙述,错误的是()
A. 有较强的变形性
B. 直径6~9μm,平均约7. 2μm
C. 起源于骨髓中红系祖细胞
D. 瑞氏染色后呈桔红色,边缘较浅,中心较深
新生儿做血细胞计数,多用下列哪个部位采血()
A. 手背
B. 耳垂
C. 足跟两侧
D. 肘部静脉
血液的PH值正常参考范围是()
A. 7. 15-7. 25
B. 7. 25-7. 35
C. 7. 35-7. 45
D. 7. 45-7. 55
A steel structure workshop (without crane and internal mezzanine floor) is designed with a span of 30 m, and there is little difference between eaves height and mid-span height, so it is most suitable for use the ( ).
A. Pitched roof symmetric portal frame
B. Propped portal frame
C. Tied portal frame
D. Mono-pitch portal frame
E. Mansard portal frame
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