问问问有关one 用法？

有这么个一道题：想问问高手one 在这是个什么东东？做什么成分？偶在做题中经常会遇到这个one做（代词？先行词？同位语？）不太清楚，所以恳请高手能帮小妹详细讲讲它的用法！感激不尽！

1、Astronomers at the Palomar Observatory have discovered a distant supernova explosion, one
            they believe to be of a type previously unknown to sciende.                                                                                                                                      详细讲讲这个句子划线为什么这个

2、     According to the Better Business Bureau, if you fail to advertise the highest price in a range of prices for a service or product as prominently as that of the lowest, it violates the New York Consumer Protection Law.

(A) if you fail to advertise the highest price in a range of prices for a service or product as prominently as that of the lowest, it

(B) if one fails to advertise the highest price in a range of prices for a service or product as prominently as the lowest price,
                    it 

(C) failure to advertise the highest price in a range of prices for a service or product as prominently as the lowest  正确答案

(D) failure to advertise as prominently the highest price in a range of prices for a service or product as the lowest

(E) failing to advertise as prominently the highest price in a range of prices for a service or products as that of the lowest

问：B中的it无法指代前面的one吗？在这的one是主语的泛指吗？

E中的that不能指代price吗？