GWD问题求帮助

Inaddition to being China’s first administrators, in thesense that they developed a coherent bureaucracy for their empire, the firstliterate culture in East Asia were the Shang, and they were well known forcrafting ornate bronze ritual vessels.

A.              the first literate culture inEast Asia were the Shang, and they were well known for crafting

B.              the first literate culture inEast Asia were the Shang, well known as the crafters of

C.              the Shang, as the first literateculture in East Asia, is well known for its crafting

D.             the Shang were the firstliterate culture in East Asia and are well known as the crafters of

E.              the Shang were the firstliterate culture in East Asia and well known

  key: D   

这句话的主语不应该是商朝吗？为什么谓语用were??我觉得正确答案C。。为什么pp08给的答案是D？？求大神指点