Answer:
When the lower esophageal sphincter is atrophied, a disease called achalasia occurs, in which there is no relaxation of the esophagus when the food is swallowed, it is difficult for the food to go down to the stomach. Some symptoms are that the food, once swallowed, can not pass and gets stuck.
Regurgitation, chest pain and weight reduction may also occur.
I believe it is class, because species are divided into different classes, but families, for example: there's the cat family, and there's the dog family. classes: the carnivores, herbivores, omnivores OR mammals, egg laying, or hermaphrodites
Canada, one of the wealthiest countries in the world, is also one of the most water-rich. The province of Ontario shares the Great Lakes—which contain 18 percent of the world’s fresh surface water—with the United States. Access to sufficient, affordable, and safe drinking water and adequate sanitation is easy for most Canadians. But this is not true for many First Nations indigenous persons. In stark contrast, the water supplied to many First Nations communities on lands known as reserves is contaminated, hard to access, or at risk due to faulty treatment systems. The government regulates water quality for off-reserve communities, but has no binding regulations for water on First Nations reserves.