SC もう一問お願いします

こんにちは。また質問させてください。
<<< >>>内が下線部と考えてください。

The growth of the railroads led to the abolition of local times, <<< which was determined by when the sun reached the observer's meridian and differing >>> from city to city, and to the establishment of regional times.

A. which was determined by when the sun reached the observer's meridian and differing
B. which was determined by when the sun reached the observer's meridian and which differed
C. which were determined by when the sun reached the observer's meridian and differing
D. determined by when the sun reached the observer's meridian and differed
E. determined by when the sun reached the observer's meridian and differing


<My Process>
A,B which は local times を指すため、was はNG。
D. differedとpassiveなのは変。
として、C,Eまで絞って、Cを選んで×。解答はEでした。
解答を見ての解釈は、「Cは、differing と不自然に進行系に
なっている部分がNG。」と言うものなのですが、この解釈で
正しいのかよく分かりません。どなたかEの方がBetterな理由を
説明して頂けないでしょうか？宜しくお願いします。