The International Youth Festival held in August 2010, was in

Mexico city
Moscow
Beijing
Tokyo

The correct answer is (c), Beijing. The 18th World Festival of Youth and Students was held in Beijing, China from August 14 to 22, 2010. The festival was attended by over 20,000 young people from over 140 countries. The theme of the festival was “For a Culture of Peace and Non-Violence for a Better World.” The festival included a variety of cultural events, such as concerts, performances, and exhibitions. There were also educational and political events, such as seminars and workshops. The festival was a success, and it helped to promote peace and understanding between young people from different cultures.

Option (a), Mexico City, is incorrect because the 18th World Festival of Youth and Students was not held in Mexico City. The 18th World Festival of Youth and Students was held in Beijing, China.

Option (b), Moscow, is incorrect because the 18th World Festival of Youth and Students was not held in Moscow. The 18th World Festival of Youth and Students was held in Beijing, China.

Option (d), Tokyo, is incorrect because the 18th World Festival of Youth and Students was not held in Tokyo. The 18th World Festival of Youth and Students was held in Beijing, China.