Which statement is not true of the performer of acupuncture?
A. He knows where to place the needles without pain.
B. He knows where the operation is to be performed.
C. He knows how to perform. the operation to cure the patient.
D. He knows how to use the needles in an operation.
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()是指一家公司以及附属的子公司和关联人之问的交易,这种交易要受到监管。
完全负相关的证券A和证券B,其中A证券的期望收益率为16%,标准差为6%,证券8的期收益率为20%,标准差为8%,如果投资A、B的比例分别为30%和70%,则证券组合的标准差为()。