OG12 SC 111 which was可否省略问题

dumengxuan

Construction of the Roman Colosseum, which was
offi cially known as the Flavian Amphitheater, began in
A.D. 69, during the reign of Vespasian, was completed
a decade later, during the reign of Titus, who opened
the Colosseum with a one-hundred-day cycle of
religious pageants, gladiatorial games, and
spectacles.
(A) which was offi cially known as the Flavian
Amphitheater, began in A.D. 69, during the reign
of Vespasian,
(B) offi cially known as the Flavian Amphitheater,
begun in A.D. 69, during the reign of Vespasian,
and
(C) which was offi cially known as the Flavian
Amphitheater, began in A.D. 69, during the reign
of Vespasian, and

这道题正确答案为C。OG给出的B选项错误的理由是begun时态错误。我想问问类似的题目表达，就是在一个核心词后面接从句或者修饰短语，C选项如果去掉which was，直接用construction，officially known as sth. ,began……这种结构对不对啊~还是说限定从句一定要加which was？

dumengxuan

可以具体说下为什么句子不清晰么？去掉which was 之后分词known是不是有修饰construction的嫌疑呀？