The correct answer is - C. Volcanic derived carbon dioxide gas bubbled from the lake and suffocated people and animals nearby.
In the summer of 1986, more specifically on the August 21st, a big tragedy happened in Cameroon. The Lake Nyos, located in the northwestern part of the country experienced a limnic eruption. This eruption triggered the release of very large amounts of carbon dioxide from the lake. The exact amount of carbon dioxide that was released is debatable, and the general consensus is that it was between 100,000 and 300,000 tons of the gas, though there are suggestions that it was up to 1.6 million tons.
The gas spread around very quickly, and being heavier than the air it stuck very low. In a radius of around 25 km from the lake, lot of people and animals were suffocated. The estimates are that 1746 people died and around 3,500 livestock died, not even counting the damage that has been done to the wild animals.
"The Midwest receives the nickname of "breadbasket" because of the abundant cereal crops it produces for the United States and the world; these crops include wheat, corn and oats. The history of staple cereal crop production in the Midwest dates back to the 1700s. The fertile soils of the Midwestern states and availability of cheap, abundant land proved suitable for launching a large-scale farming effort, ultimately leading to high volume production of predictable and reliable crops" credit to google put it in ur own word
B. Topic is under plate tectonics and involves divergence,convergence and transform plate boundary:)
