Final answer:
The Qing dynasty did not incorporate Korea into its territory; Korea was a separate kingdom during the Qing dynasty's rule.
Step-by-step explanation:
The Qing dynasty incorporated various regions into China's territory but some areas remained independent. The correct answer to which area was not incorporated by the Qing dynasty is c) Korea. Korea existed as a separate kingdom, known as the Joseon kingdom, until it was annexed by Japan in the early 20th century. The Qing dynasty did incorporate areas such as Tibet in 1720 and Xinjiang in the mid-18th century. Vietnam was a tributary state for much of its history but was not formally incorporated into the Qing Empire.