The Tragedy at Lake Nyos in Cameroon,West Africa,was Caused By

The tragedy at Lake Nyos in Cameroon,West Africa,was caused by:

A) the release of excessive amounts of nitrogen gas that had been dissolved in the water at the bottom of the lake.
B) the release of excessive amounts of oxygen gas that had been dissolved in the water at the bottom of the lake.
C) the release of excessive amounts of carbon dioxide that had been dissolved in the water at the bottom of the lake.
D) the release of excess water stored in the volcanic lake which flooded the village below.
E) none of the above