协方差分析中，处理间比较要采用SAS软件中的MEANS方法。

A. DAS是对已有的服务器存储能力的简单扩展

B. NAS是在网络的环境中，为用户提供文件级的存储服务

C. SAN在传输中主要采用速率可以达到Mbps量级的SCSI与光纤通道技术

D. SAN将网络中多个私有的存储空间整合起来，提高了存储设备的利用率

A、input x@

B、input x$@

C、input x@@

D、input x$@@

A rapid means of long-distance transportation became a necessity for the United States as settlement (新拓居地) spread ever farther westward. The early trains were impractical curiosities, and for a long time the railroad companies met with troublesome mechanical problems. The most serious ones were the construction of rails able to bear the load, and the development of a safe, effective stopping system. Once these were solved, the railroad was established as the best means of land transportation. By 1860 there were thousands of miles of railroads crossing the eastern mountain ranges and reaching westward to the Mississippi. There were also regional southern and western lines.

The high point in railroad building came with the construction of the first transcontinental system. In 1862 Congress authorized two western railroad companies to build lines from Nebraska westward and from California eastward to a meeting point, so as to complete a transcontinental crossing linking the Atlantic seaboard with the Pacific. The Government helped the railroads generously with money and land. Actual work on this project began four years later. The Central Pacific Company, starting from California, used Chinese labor, while the Union Pacific employed crews of Irish laborers. The two groups worked at remarkable speed, each trying to cover a greater distance than the other. In 1869 they met at a place called Promontory in what is now the state of Utah. Many visitors came there for the great occasion. There were joyous celebrations all over the country, with parades and the ringing of church bells to honor the great achievement.

The railroad was very important in encouraging westward movement. It also helped build up industry and farming by moving raw materials and by distributing products rapidly to distant markets. In linking towns and people to One another it helped unify the United States.

The major problems with America's railroad system in the mid 19th century lay in ______.

A．poor quality rails and unreliable stopping systems

B．lack of financial support for development

C．limited railroad lines

D．lack of a transcontinental railroad

A、数据行前使用datalines，数据行后使用“;”

B、数据行前使用datalines，数据行后使用“;;;;”

C、数据行前使用datalines4，数据行后使用“;;;;”

D、数据行前使用datalines4，数据行后使用“;”

A、monohybrid crosses will show segregation and independent assortment

B、the segregation of alleles of one gene depends on the segregation of all other alleles

C、test crosses always produce heterozygous offspring

D、alleles of different genes segregate at random and fertilization is random

E、alleles segregate at meiosis

A、proc corr data = sas；表示对数据集sas进行pearson相关分析

B、var x y; 表示对变量x与y 之间进行相关分析

C、partial 语句是指定计算变量间的偏相关系数

D、with语句与var 语句配对，表示计算with指定的变量与var指定的每一个变量进行相关分析