某企业有三种现金持有方案，它们各自的机会成本、管理成本和短缺成本见下表，机会成本为该

A Sports体育运动
Many animals engage in play，but homo sapiens is the only animal (1) have invented sports.Since sports are an invention，a part of culture (2) than an aspect of nature，all definitions of sports are somewhat arbitrary. (3) sports are a human universal found in every known culture or a (4) unique to modern society depends upon one’s definition of sports.Men and (5) have always run，jumped，climbed，lifted，thrown， and wrestled，but they have (6) always performed these physical activities competitively. Although all literate societies seem to (7) contests of one sort or another in which men， and sometimes women， (8) in displays and tests of physical skill and prowess，sports may be (9) defined as physical contests performed for their own sake and not for (10) ulterior end.According to this strict definition，neither Neolithic hunters nor contestants (11) religious ceremonies such as the ancient Olympic Games were engaged in sports. (12) on the stipulation that sports must be performed for their own sake (13) the paradoxical elimination of many activities which are usually thought of as (14) ，such as exercises done for the sake of cardiovascular fitness，races run (15) satisfy a physical education requirement，ball games played to earn a paycheck. (16) definition also means abandonment of the traditional usage in which"sport，"derived (17) Middle English disporter，refers to any light hearted recreational activity.In the. (18) of some 18th- century aristocrats，a game of backgammon and the seduction of (19) milkmaid were both considered good sport，but this usage of the term (20) become archaic.

宫颈黏液出现羊齿状结晶，相当于月经周期的（）

A.第6～7天

B.第9～10天

C.第12～13天

D.第15～16天

E.第18～19天

记忆是复杂的心理活动的过程，其特点不包括（）

A.有意注意

B.再认和重现

C.保持

D.识记

E.随年龄的增长而增长

患者，女性，20岁，诉自小牙齿不好，要求牙体美容。检查：全口牙齿均有Ⅰ～Ⅱ度磨耗，牙冠均呈微黄色，釉质缺损较严重，牙本质暴露，探诊、温度测试均无明显反应。患者诉外祖母和母亲的牙齿也有类似的情况。

拟诊（）

A.釉质发育不全

B.四环素牙

C.遗传性乳光牙本质

D.牙本质过敏

E.磨耗

空洞为主型的继发性肺结核CT征象为（）

A.肺段或肺叶高密度阴影，内可见单个或多个空洞

B.病变同侧和对侧肺野内散在新旧不一的支气管播散病灶

C.空洞病灶周围有较多的条索状致密影，并常见钙化

D.肺纹理粗乱扭曲，可见支气管扩张征象

E.常伴较明显的胸膜肥厚及相应部位的胸廓塌陷