系统的基本属性不包括（）。 A.整体性 B.独立性 C.动态性 D.目的性 E.层次

The nurse is caring for a toddler with Down syndrome. To help the toddler cope with painful procedures, the nurse can（）

A. prepare the child by positive self-talk.

B. establish a time limit to get ready for the procedure.

C. hold and rock him and give him a security object.

D. count and sing with the child.

如图将一金属薄片垂直置于磁场B中，在薄片的两个侧面a、b间通以电流I时，另外两侧c、f间产生电势差，这一现象称为霍尔效应。且满足U＝kIB/d，式中d为薄片的厚度，k为霍尔系数。回答下列问题

（1）关于c、f两侧面哪面的电势较高？     （填  c或f ）；

（2）其他条件不变，只增加磁感应强度B的大小，霍尔电压U_m会怎样变化？     （填增大或减小）

与3a²b是同类项的是（ ▲ ）

A．a²

B．2ab

C．3ab²

D．4a²b

Those who________the plan tried to persuade those who didn't agree to it. [      ]

A. was against  

B. was for

C. were against  

D. were for

中华历史上最早的官办学府是（）在位期间设立的太学。