Q: This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
Passage: In 1822, the American Colonization Society began sending African-American volunteers to the Pepper Coast to establish a colony for freed African Americans. By 1867, the ACS (and state-related chapters) had assisted in the migration of more than 13,000 African Americans to Liberia. These free African Americans and their descendants married within their community and came to identify as Americo-Liberians. Many were of mixed race and educated in American culture; they did not identify with the indigenous natives of the tribes they encountered. They intermarried largely within the colonial community, developing an ethnic group that had a cultural tradition infused with American notions of political republicanism and Protestant Christianity.
A:
In what year did volunteers leave the Pepper Coast?