问题
单项选择题
树木种植中一般大灌木所必须的最低土层厚度为（）厘米。
A．45
B．60
C．90
D．150
答案
参考答案：B
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树木种植中一般大灌木所必须的最低土层厚度为（）厘米。
A．45
B．60
C．90
D．150
参考答案：B
John McHenry is a junior consultant working in Oldie Village Pension Consulting. He has calculated annual returns for 300 portfolio managers, and is analyzing the relationship between fees and performance. The dataset he is using (returns and fees for each manager) is an example of:
A．
| A. a stratified random sample. |
B．
| B. a normalized dataset. |
C．
| C. a cross-sectional dataset. |