intended primarily to stimulate family summer travel, the new airfare, which allows both an adult and a child to fly for the price of one ticket, and also shortens the advance-purchase requirement for family travel to a minimum of seven days rather than fourteen.

(c)also shortens the advance-purchase requirement for family travel to a minimum of seven days rather than that of

(E)also shortens the advance-purchase requirement for family travel to a minimum of seven days rather than

(c)that 指代 a minimum 答案说少了介词to(感觉并列题中若动词后又介词，and 后就一定要加介词，不知道这种感觉对伐), 且原意改变了，但我觉得意思是从最短需要14天改到最短需要7天，没改变意思啊

且求教什么时候要加"that of ",什么时候不需要加"that of "

我现在的观点是rather than前后要有平行的内容就行, 这里fourteen清楚的表明是fourteen days, 前面的a minimum of 用that of代替显得多余罗索, 可省。供参考，再讨论。

rather than不是比较句中的than，如果a minimum of sth.1....比较级 than that of sth.2这里的that of 不能随意省否则比较对象不一致。

供参考，再讨论。