在螺杆上安装两个螺母，先装的叫（），后装的叫副螺母.

现有一列数据，它们是4，4，5，3，5，5，2。这列数据的平均数、众数和全距依次是（）。

A．4，4，2

B．4，5，3

C． 5，4，4

D． 5，5，1

将标准系列溶液测得的吸光度值对六价铬含量作图，即得标准曲线。

Charles Darwin wed his cousin Emma and spawned 10 children, including four brilliant scientists. Albert Einstein’s second wife Elsa was his first cousin. Queen Victoria said “I do” to hers. So have millions worldwide. In parts of Saudi Arabia, 39% of all marriages are between first cousins.

In the U. S., though, the practice bears a stigma of inbreeding just this side of incest. The taboo is not only social hut legislative; 24 states ban the marriage of first cousins: five others allow it only if the couple is unable to bear children. A major reason for this ban is the belief that kids of first cousins are tragically susceptible to serious congenital illnesses.

That view may have to change. A comprehensive study published recently in the Journal of Genetic Counseling indicates such children run an only slightly higher risk of significant genetic disorders like congenital heart defects — about two percentage points above the average 3% to 4%. Says the study’s lead author, Robin Bennett, president-elect of the National Society of Genetic Counselors, which funded the study: “Aside from a thorough medical family history, there is no need to offer any genetic testing on the basis of consanguinity alone”.

Publication of the study will do more than tweak public awareness; it will enlighten doctors who have urged cousin couples not to have children. “Just this week,” says Bennett, “I saw a 23-year-old woman who had had a tubal ligation because her parents were cousins and her doctor told her she shouldn’t have children.”

The American proscription against cousin marriages grew in the 19^th century as wilderness settlers tried to distinguish themselves from the “savage” Indians, says Martin, author of the book Forbidden Relatives: The American Myth of Cousin Marriage. “The truth is that Europeans were marrying their cousins and Native Americans were not.”

And doesn’t God have stern words on the subject Christie Smith, 37, a Nevada writer, says she felt guilty when she fell in love with her first cousin’s son Mark. “I was trying so hard to convince myself not to have these feelings,” she recalls, “that I went to the Bible looking for confirmation that it was wrong. And what I found was the exact opposite: support for cousin marriages.” The patriarch Jacob married two of his first cousins, Rachel and Leah. Smith married Mark in 1999.

The medical ban is lifted; the social stain may take longer to disappear.

It can be inferred from the last paragraph that（）

A. the ban on cousin marriages is lifted

B. cousin marriages are permitted again

C. the prejudice against cousin marriages dies hard

D. cousin marriages may not be as bad as people think

有关人际传播的描述错误的是( )

A．是全身心的传播
B．人际传播的信息所覆盖的人群不及大众传播
C．是人们面对面的进行信息和情感的交换
D．在传播过程中，不宜再调整和更改已经确定好的传播策略、交流方式及内容
E．以个体化信息为主

检定变送器时，试验点和标准值是如何确定的？