杂质在硅中扩散主要采用两种方式：恒定表面源扩散和限定表面源扩散，下面对其叙述正确的有
A. 恒定表面源扩散指将硅片处于恒定浓度的杂质氛围中，杂质扩散到硅表面很薄的表层。
B. 恒定表面源扩散特点：可控制表面浓度和扩散探度，但不能任意控制杂质总量，因而难以制作出高表面浓度的浅结
C. 限定表面源扩散指在扩散过程中硅片外部无杂质的环境氛围下，杂质源限定于扩散前淀积在硅片表面极薄层内的杂质总量Q，扩散过程中Q为常量，依靠这些有限的杂质向硅片内进行的扩散。
D. 限定表面源扩散特点：控制杂质总量和扩散深度，但不能任意控制表面浓度，难以制作出低表面浓度的深结
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在16位的PC机上使用C语言，若有如下定义：struct data{int i;char ch;double f;} b;则结构变量b占用内存的字节数是（）。
A. 1
B. 2
C. 8
D. 11
以下程序输出结果是（）#include typedef union{ long i;int k[5];char c;} DATE;struct date{ int cat;DATE cow;double dog;} too;DATE max;main(){ printf（"%d\n",sizeof（struct date）+sizeof（max））;}
A. 25
B. 30
C. 18
D. 8
Most economists believe that classical economic theory is a good description of the world in
A. the long run, but not in the short run.
B. the short run, but not in the long run.
C. the short run and in the long run.
D. neither the short nor long run.
Business cycles
A. are explained mostly by fluctuations in corporate profits.
B. no longer are very important due to government policy.
C. are fluctuations in real GDP and related variables over time.
D. All of the above are correct.
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