Modem的作用是
A.把计算机信号和音频信号互相转换
B.把计算机信号转换为音频信号
C.把音频信号转换为计算机信号
D.防止外部病毒进入计算机中
参考答案:A
急性非特异性心包炎可能的主要病因是()。
A.病毒
B.结核分枝杆菌
C.立克次体
D.细菌
E.真菌
An analyst does research about exchange trade funds (ETFs). Which of the following statements is least accurate to describe exchange trade funds' characteristics()
A. Portfolio holdings of ETFs are transparent.
B. ETF's structure prevents a significant premium or discount to NAV.
C. Dividends are reinvested annually for open-end ETFs.