Answer:
Carbon Dioxide
Step-by-step explanation:
Trust me its correct but for those who are hesitant
---> In 1986, possibly as the result of a landslide, Lake Nyos suddenly emitted a large cloud of CO2(Which is Carbon Dioxide), which suffocated 1,746 people and 3,500 livestock in nearby towns and villages, the most notable one being Chah, which was abandoned after the incident.