螺旋结构是自然界最普遍的一种结构。下列与生命的螺旋结构相关的叙述正确的是[ ]

A．螺旋藻是蓝藻的一种，其细胞内进行光合作用的部位是叶绿体

B．生活在人体胃部的幽门螺旋杆菌主要是通过有氧呼吸方式供能

C．在真核细胞有丝分裂过程中，染色质高度螺旋形成染色体

D．DNA双螺旋结构的基本骨架由核糖和磷酸交替排列组成

An economist concluded that Kregg Company deliberately discriminated against people with a history of union affiliation in hiring workers for its new plant. The economist’s evidence is that, of the 1,500 people hired to work at the new plant, only 100 had ever belonged to a labor union, whereas in Kregg Company’s older plants, a much higher proportion of workers have a history of union affiliation.
Which of the following is an assumption on which the economist’s argument depends

A．None of the people with a history of union affiliation who were hired to work at the new plant were union organizers.

B．Applicants for jobs at the new plant were not asked by Kregg’s recruiters whether they had every belonged to a labor union.

C．In the plants of some of Kregg’s competitors, the workforce consists predominantly of union members.

D．The company believes that the cost of running the new plant will be lower if labor unions are not represented in the workforce.

E．(E) The pool of potential candidates for jobs at the new plant included some people, in addition to those Kregg hired, with a history of union affiliation.