短波传播存在寂静区，其圭要原因是（）。
A. 地波传播，因发射台太远信号衰减，接收台收不到
B. 天波传播存在跃距，且跃距大于地波传播的最大距离
C. 天波传播的多径传播引起衰减
D. A+B
皮脂腺多位于（）和（）之间，为（），腺泡的周边部是一层较小的（），腺泡中心细胞较大，胞质中充满（）。
为研究产品销售额与销售利润之间的关系，某公司对所属6家企业进行了调查，设产品销售额为x（万元），销售利润为y（万元）。调查资料经初步整理和计算，结果如下：∑x=225∑x2=9823∑y=13∑y2=36.7∑xy=593要求：（1）计算销售额与销售利润之间的相关系数；（2）配合销售利润对销售额的直线回归方程。（3）解释回归系数的含义
You need to design an access control strategy for the financial data used by the accounting department. Your solution must meet business requirements. What should you do？（）
A. Modify the properties of the computer object named P_FS2 to enable the Trust computer for delegation attribute. Instruct accounting department users to use Encrypting File System （EFS） to encrypt files
B. Modify the properties of all accounting department user accounts to enable the Account is trusted for delegation attribute. Instruct accounting department users to use Encrypting File System （EFS） to encrypt files
C. Modify the properties of accounting department computers to enable the Trust computer for delegation attribute. Configure accounting department client computers to use IPSec to communicate with P_FS2
D. Modify the properties of all administrator accounts in the forest to enable to Account is trusted for delegation attribute. Configure accounting department client computers to use IPSec to communicate with P_FS2
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