Q20:

Construction of the Roman Colosseum, which was officially 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.

1. which was officially known as the Flavian Amphitheater, began in A.D. 69, during the reign of Vespasian,
2. officially known as the Flavian Amphitheater, begun in A.D. 69, during the reign of Vespasian, and
3. which was officially known as the Flavian Amphitheater, began in A.D. 69, during the reign of Vespasian, and
4. officially known as the Flavian Amphitheater and begun in A.D. 69, during the reign of Vespasian it

E. officially known as the Flavian Amphitheater, which was begun in A.D. 69, during the reign of Vespasian,

ANS C 我选B , 请大家帮忙

根据句意,本句应使用过去时.began 是begin 的过去时,begun 是 begin的过去分词,因此选c.