企业拟进行一项投资，投资收益率的情况会随着市场情况的变化而发生变化，已知市场繁荣、一般和衰退的概率分别为0.3、0.5、0.2。如果市场是繁荣的那么投资收益率为20%，市场情况一般则投资收益率为10%，市场衰退则投资收益率为-5%，则该项投资的投资收益率标准差为()。
A. 0.1
B. 0.09
C. 0.0866
D. 0.07
查看答案
How many chickens did Mary's uncle send her？
A. Eleven.
B. Six.
C. Five.
According to information provided by the passage, which of the following traits would the
Affectionate
B. Abusive
C. Pragmatic
Deceitful
E. Antagonistic
A．migrantsB．racistsC．immigrantsD．blacks
A. migrants
B. racists
C. immigrants
D. blacks
Why couldn't Tom and Judy find out who sent them the tickets？
A. Their friends wanted to keep it a secret.
B. The letter with the tickets was not signed.
C. There was no letter with the tickets.
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