按照投资者的共同偏好规则，可以排除那些被所有投资者都认为差的组合，把排除后余下的这些组合称为有效证券组合。 ( )
参考答案：对
某物质经鉴定只含有一种元素，下列说法正确的是[ ]
A.肯定是纯净物
B. 肯定是某一种单质
C. 可能是混合物
D.一定是一种稀有气体
The song "In Spring"___ original singer is Wang Feng has brought national fame to Xuriyanggang, ____
won the second place in the 2010 Avenue of Stars Finals. [ ]
A. who; whose
B. which; who
C. whose; who
D. of whom; who
