Question

The decline of Tibet as a powerful kingdom happened? a. at the same time as the decline of the Tang dynasty b.during the Sui dynasty c. after the collapse of the Tang dynasty d. before the decline of the Tang dynasty
Ms. Sue
We'll be glad to check your answer.
Ms. Sue
Your answer isn't supported by this article.

http://en.wikipedia.org/wiki/Tuyuhun_Kingdom

How does your book define Tibet as a powerful kingdom?