在Excel中，可以通过“视图”菜单显示或隐藏工具栏，但编辑栏却不可能被隐藏。 (

A mutual fund manager wants to create a fund based on a high-grade corporate bond index. She first distinguishers between utility binds and industrial bonds; she then, for each segment, defines maturity intervals of less than 5 years, and greater than 10 years. For each segment and maturity level, she classifies the bonds as callable or non-callable. For the manager’s sample, which of the following best describes to:sampling approach number of sampling cells（）

A. simple random sample 3

B. simple random sample 12

C. stratified random sample 12

下列费用不属于直接费的是（）。

A、直接工程费

B、规费

C、企业管理费

D、措施费

脓胸、脓气胸的肺炎（）

A.葡萄球菌肺炎

B.腺病毒肺炎

C.毛细支气管炎

D.支原体肺炎

E.支气管肺炎

采掘工作面风流中瓦斯浓度达到多少时必须停止工作，撤出人员，切断电源进行处理？

低钾血症中哪一项论述是错误的？（）

A.血清钾低于3.8mmol／L

B.钾丧失过多

C.钾摄入不足

D.心肌兴奋性增高

E.肠麻痹