CULTURE 的单复数问题

mcaquamiao

In addition to being China’s first administrators, in the sense that they developed a coherent bureaucracy for their empire, the first literate culture in East Asia were the Shang, and they were well known for crafting ornate bronze ritual vessels.

这是语法prep08里的一个例子。想请问明白的同学，CULTURE是个复数意义的名词么？我去语法相关的网页上找了，但有cultures这个用法。谢啦！

这个选项里是没有was的，不然那是多大的迷惑性啊。