询问一题语法

再一题SC  OA是B  部是很理解为什么会用原形的be 而不是用跟前面一样的过去时态呢
                (was, bega…)  我自己的选择是E

1. During the nineteenth century it was common practice for museums and collectors to reframe all their pictures uniformly, a custom that began after Napoleon ordered that all paintings in the Louvre are given new frames in the fashionable Empire style.

(A) are given new frames in the fashionable
(B) be given new frames in the fashionable
(C) are newly framed in the fashion of the
(D) will be newly framed in the fashion of the
(E) were given new frames in the fashionable