求解一道英语选择题的解析过程

题目

求解一道英语选择题的解析过程
Some teaching equipment,together with books and pens,----offered to the destroyed schools after the flood.
A.was B.are C.were D.had been offered
Some teaching equipment不是复数吗，为什么要选A而不选C呢？

答案

A
after the flood时间状语,类似two days ago也是.所以用过去式,排除B、D.
together...是插入语,主语是Some teaching equipment,很明显单数
所以选A
i.e.
I ,together with my parents,watched a film after the party.