This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Q: Passage: On November 13, 1988, approximately 10,000 people attended an officially sanctioned meeting organized by the cultural heritage organization Spadschyna, the Kyiv University student club Hromada, and the environmental groups Zelenyi Svit ("Green World") and Noosfera, to focus on ecological issues. From November 1418, 15 Ukrainian activists were among the 100 human-, national- and religious-rights advocates invited to discuss human rights with Soviet officials and a visiting delegation of the U.S. Commission on Security and Cooperation in Europe (also known as the Helsinki Commission). On December 10, hundreds gathered in Kiev to observe International Human Rights Day at a rally organized by the Democratic Union. The unauthorized gathering resulted in the detention of local activists. Question: What did people gather to observe on December 10th?
A:
International Human Rights Day