Answer:
Comparing Medieval Japan, Korea, and Vietnam
Description 1 applies to Korea.
Description 2 applies to Vietnam.
Description 3 applies to Japan.
Explanation:
The Todaiji Temple is located in Japan. This sets description 3 apart for Japan. The southern kingdom refers to Vietnam located in the South-east Asia. Vietnam is known to have been ruled by China for over a thousand years, and the Vietnamese language is written based on Chinese characters. This matches with description 2. Korea, which is located in the Northeast Asia, matches description 1. Moreover, the Korean language is a multisyllabic language, unlike the Chinese that is monosyllabic.