Where was there extensive ethnic cleansing in the 1990s?
Ethnic cleansing is the involuntary removal of an ethnic group from a territory, in order to create a homogenous population. Ethnic cleansing sometimes happens without much violence, but it usually entails widespread attacks on a community in order to drive them out, and it always involves at least the threat of force. Note that ethnic cleansing is somewhat different from genocide; unlike genocide, which is usually committed by a government, ethnic cleansing can be committed…
Atheism is the lack of belief in deities and is not connected to ethnic cleansing at all. Ethnic cleansing could be believed to be something a deity calls for so, in that manner, theism (belief in deities) is more connected to ethnic cleansing than atheism. It's possible for atheists to engage in ethnic cleansing but they do it for reasons other than atheism.
Which of the following describes a major difference between the international response to genocide in Bosnia and Rwanda?
There have been several ethnic cleansings/genocides in modern Turkish history. The largest was the Armenian Genocide with 1.8 million Armenians murdered. There were also a number of massacres of Greek civilians during the Balkan Wars and the War of Turkish Independence. During the 1980s to the present, there has been repression and cultural cleansing of the Kurds. (However, the Kurds were not murdered en masse, so there was no ethnic cleansing per se.)