OG12 23 平行 题目已可见

In a previous design, the weight of the discus used in
track competition is concentrated in a metal center, but
now it is lined with lead around the perimeter, thereby
improving stability in flight and resulting in longer
throws.
?? (B) According to a previous design, the weight of the
discus used in track competition was concentrated in a
metal center, but now it is
?? (C) Once designed with its weight concentrated in a
metal center, the discus used in track competition is
now
?? (D) The discus used in track competition, once designed
with its weight concentrated in a metal center, but now
?? (E) The discus used in track competition was once
designed having its weight concentrated in a metal
center and now
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A选项后面给的解释是It指代的是weight所以错了，是因为but前后两个句子要平行，所以它们两句话的主语如果有指代的话则也要是一直的么？不然的话it 不是可以指代discus吗？      如果是这个原因，那and是否也是这样？还有哪些词也这样？

有道理，但是还有一道题
To Josephine Baker, Paris was her home long before it
was fashionable to be an expatriate, and she remained
in France during the Second World War as a
performer and an intelligence agent for the
Resistance.
?? (A) To Josephine Baker, Paris was her home long
before it was fashionable to be an expatriate,
?? (B) For Josephine Baker, long before it was
fashionable to be an expatriate, Paris was her home,
?? (C) Josephine Baker made Paris her home long before
to be an expatriate was fashionable,
?? (D) Long before it was fashionable to be an expatriate,
Josephine Baker made Paris her home,
?? (E) Long before it was fashionable being an expatriate,
Paris was home to Josephine Baker,


要求的也是and 前后平行的话最好主语都是人，那是否平行的时候就有这个要求呢？