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问题 单项选择题

男性，13岁，左肘肿胀、疼痛1个月，疼痛以夜间为重，无发热。CT冠状重建如图。应首先考虑的诊断是（）

A．骨髓炎

B．骨样骨瘤

C．骨脓肿

D．软骨瘤

E．嗜酸性肉芽肿

答案

参考答案：B

解析：

骨样骨瘤的瘤巢呈圆形或椭圆形，直径多在0.1～1.5cm，由血供丰富的结缔组织、放射状骨样小梁、不同程度的钙化和骨化组成。

阅读理解

Box Office Instructions
Discounts/ Service charges:
We offer children (12 and under), seniors (65 and over) and students (student ID card required) discounts on all seats. Please call the Box Office to know about any other possible discounts.
Returns/ Exchanges:
We are happy to offer returns or exchanges of tickets bought up until the close of the last business day before the show with a $3.00 per ticket fee for this service. The box office must be informed directly in order to exchange tickets to another date (this service is not available online).
Friendly reminders:
Latecomers will not be permitted to enter the hall until a suitable break in the performance.
Children must be seated where they can be looked after by parents.
Please show consideration for other audiences by not talking during the performance, and please encourage children to do the same.
Cameras and recording equipment are not allowed to be used in our theatre.
Please turn off all cell phones while enjoying the performance.
Will call:
Please tell us at the time of booking if you would like your tickets mailed to you, otherwise they will be held for pickup at the box office.
小题1:We can learn from the passage that exchanges of tickets bought ________.
A．are free of chargeB．are not available until the last business day
C．will not be given a big cash discountD．need to contact the box office directly
小题2:Which of the following statements is TRUE according to the passage?
A．Latecomers will not be permitted to enter the theatre.
B．There is a special area for children in the theatre.
C．The audience is not allowed to take photos in the theatre.
D．Children can talk in a low voice during the performance.
小题3: According to the passage, the audience ________.
A．can receive their tickets by mailB．can see the performance online
C．can’t take cell phones to the theatreD．can’t return tickets in any case
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填空题

设随机变量X服从参数为1的指数分布；随机变量

则方差DY=______．
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