慢心肺心病急性发作期最常见的诱因是（）
A、过度劳累
B、大量利尿剂
C、应用镇静剂
D、呼吸系统感染
参考答案：D
二级，甲乙级美发厅混合照度应（）。
A.不低于250lx
B.不低于200lx
C.不低于150lx
D.不低于100lx
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.
