当供暖管道温度大于100℃时，其与可燃物之间采取的措施是（）。 A.距离不小于150

关于“子宫输卵管造影价值”，下列说法错误的是

A．观察子宫、输卵管发育情况

B．了解输卵管是否通畅

C．诊断输卵管慢性炎症

D．可间接判断有无盆腔炎

E．无治疗价值

假设A证券的预期报酬率为20%，标准差为40%；B证券的预期报酬率为12%，标准差为13.3%。投资者将25%的资金投资于A证券，将75%的资金投资于B证券。

[要求]

（1）计算该组合的预期报酬率；

（2）若AB证券完全正相关，计算该组合的标准差；

（3）若AB证券完全负相关，计算该组合的标准差；

（4）若AB证券不完全正相关，相关系数为0.4，计算该组合的标准差；

（5）若AB证券不完全负相关，相关系数为-0.4，计算该组合的标准差；

（6）计算完全投资于A和完全投资于B的预期报酬率和标准差；

（7）根据计算结果作出简要说明。

轿车底盘检查有哪些内容？

(五)

TOKYO-Our kids, the Japanese government announced, have forgotten how to behave. They can’t be bothered with housework. If they see someone being wronged, they probably look the other way.

Few countries have placed more importance on being well-behaved in public than Japan. The simplest requests for directions often result in guided tours. Smiling shopkeepers are still the rule. Lost wallets usually make their way to their owners.

But according to recent surveys, all that may be going the way of the ancient hair-do. And Japan’s government has gone into something of a crisis mode.

A Japanese Education Ministry Survey formed late in 1999 and made public last month found that Japan moves behind other nations in teaching youngsters right from wrong.

It also reported that Japanese children are less helpful and do far less housework than their foreign peers in all classes. But they are better about taking dirty dishes to the kitchens after dinner.

In addition, Japanese kids are more likely to dry their hair and carry cell phones than American and Chinese kids, according to another survey, by a Tokyo-based tank.

Children in about 8 percent of public school classrooms are so disorderly that teachers cannot hold lessons, further recent reports show. children refuse to sit, to listen or to stop talking.

Older and middle-aged Japanese continue to have a solid sense of good manners and social justice, says Professor Yoshina Hirano from Shinshu University, who was appointed to direct the ministry’s survey.

Despite the knowledge of good manners among adults, the breakdown in manners may be spreading, he said.

The second paragraph seems to show us that （）.

A．the education system of Japan is better than that of any other country

B．shopkeepers in Japan are too kind to their customers

C．Japanese kids often find wallets on their way to their schools

D．Japanese adults in public places act politely to each other

统计学研究的基本特点是（）

A、从数量上认识总体单位的特征和规律

B、从数量上认识总体的特征和规律

C、从性质上认识总体单位的特征和规律

D、从性质上认识总体的特征和规律