关于肠溶片的叙述，错误的是A．胃内不稳定的药物可包肠溶衣 B．强烈刺激胃的药物可包肠

有关糖类的叙述中，正确的是 [ ]

A．糖类是具有甜味的物质

B．糖类是具有C_n(H₂O)_m通式的物质

C．糖类是含有醛基或羰基的物质

D．糖类一般是多羟基醛或多羟基酮以及能水解产生它们的物质

使用有机材料制成的薄膜，给环境造成的“白色污染”十分严重。我国最近研制成功的一种可降解塑料结构如下：

A． B． C．

该塑料有良好的生物适应性和分解性，能自然腐烂分解。试回答下列问题：

(1)这种可降解塑料A、B、C的链节所对应的三种单体依次是 a________， b________， C________。

(2)可降解塑料在自然界可通过___________ （填反应类型）反应分解为a、b、c三种小分子有机物。

(3)单体a和c各1 mol在浓硫酸存在和加热条件下，可生成含有六元环的环状化合物，写出有关反应的化学方程式 _________________。

(4)单体b在NaOH溶液中可发生消去反应生成不饱和羧酸，此不饱和羧酸的结构简式是_________ 。此不饱和羧酸属于链状羧酸的同分异构体还有__________种。

导致脉压增大的疾病是

A．缩窄性心包炎

B．心力衰竭

C．低血压

D．主动脉瓣关闭不全

E．主动脉瓣狭窄

配管配线工程中，当选用钢管明配时，其连接方式应为( )。

A．对口焊接

B．卡套式连接

C．管箍丝接

D．卡箍式连接

An analyst does research about expected return and expect standard deviation of return from investment portfolio. Two assets have the same expected return and the same expected standard deviation of returns. The correlation coefficient of returns between the two assets is expected to be +0.6. Which of the following statements best describes the standard deviation of a portfolio composed of those two assets
If the two assets are combined to form a portfolio, the expected standard deviation of that portfolio will be:（）

A. the same as the expected standard deviation of returns for each asset because the correlation coefficient of returns is positive.

B. less than the expected standard deviation of returns for each asset because the correlation coefficient of returns is less than +1.0.

C. unaffected by the portfolio weights used for each of the two assets because the assets have the same expected return and the same expected standard deviation of returns.