The statement that best explains why the Hutu-led government in Rwanda tried to kill the Tutsi population during their civil war is:
The Tutsi-led rebel group was trying to overthrow the government.
This reflects the context of the Rwandan Civil War (1990-1994), where the Tutsi-led Rwandan Patriotic Front (RPF) was indeed engaged in conflict with the Hutu-led government, which perceived the RPF's actions as a direct threat to its power and control. This led to a genocidal campaign against the Tutsi population.