男性，37岁。规律性上腹痛2年，加重1周，2小时前排暗红色稀便约500ml，站立时眼

I want to have a pen friend, hopeful a girl in her early twenties, and with interests similar with mine. In my mind, she is someone who are interested in travelling, swimming, and play table tennis. Besides, it would be better for her to have pet dog as I keep one at home for some time.

Although we are thousand of miles away from each other, but I can share with her our travelling experiences, taking care of pets, or whatever we had in common. And I believe I will improve her English by doing so and learns more about her country.

某市调查了100例正常人的血铅含量（μg/100g），其频数分布呈正偏峰分布。

表示集中趋势应选什么指标（）。

A.算术均数

B.几何均数

C.中位数

D.众数

E.标准误

剥脱性皮炎型药疹的特点哪项描述不正确？（）

A.可伴药物性肝炎

B.大量脱屑

C.初次发病潜伏期约一周

D.病程反复长达数月

E.可累及黏膜

[蒙古源流]的作者是（）。

由于建设工程实施过程中的每个变化都会对目标和计划的实现带来一定的影响，所以，控制人员需全面、及时、准确地了解计划的执行情况及其结果，这就需要通过( )来实现。

A．转换
B．反馈
C．对比
D．纠正