计算矩形截面混凝土梁的受剪承载力时，应采用混凝土的( )强度取值。

黄曲霉毒素经动物胃肠吸收后主要毒害的器官是：A、肝脏B、肾脏C、肺脏D、胰脏E、心脏

单项选择题黄曲霉毒素经动物胃肠吸收后主要毒害的器官是：A、肝脏B、肾脏C、肺脏D、胰脏E、心脏

在砖墙在高出室外地坪100mm以上，低于室内地面一皮砖处，设水泥砂浆防潮层，下列图示构造，哪一种做法设计不当？...

单项选择题在砖墙在高出室外地坪100mm以上，低于室内地面一皮砖处，设水泥砂浆防潮层，下列图示构造，哪一种做法设计不当？( )

Enough sleep is important to health. The amount of slee...

单项选择题Enough sleep is important to health. The amount of sleep（21）depends on the age of the per-son and the conditions in which sleep（22）. The young may need more sleep than the old, but generally eight hours are enough for the health of grown-ups. Some can（23）with less than this amount but（24）may need more. Every person knows his own need. It is then a matter of how to（25）it. Sleep should always be enough to make one relaxed(松弛)and ready for（26）work.
Fresh air is（ 27）to sound sleep(酣睡). It is not without reason for some people to（28）that it is practical to sleep in the open air.（29）a person can keep himself warm, out-of-door sleeping probably gives the body（30）complete relaxation.
Ability to sleep is largely a habit. The conditions referred to only lead to sleep. Out-of-door（ 31）,a good habit of regular drinking and the avoidance of late eating and（32）are all helpful to sound sleep. Such factors are largely within the control of any person. A bath at（33）, neither hot nor cold but of（34）temperature, may be helpful to sleep. Sleeping pills should never be taken except when suggested by（35）.
第（31）题选