—Tom hadn’t worked hard and failed in the exam. But he said that was because the problems were too hard.

—That is “    .”

A．a great talker is a great liar.

B．a man can do no more than he can

C．a bad workman always blames his tools

D．It is not work that kills, but worry

某投资者投资的资产由2种增为50种，下列无法因这种做法而降低的风险是( )。

A．市场风险
B．独特风险
C．特定公司风险
D．非系统风险