Why is cholera still a problem for many countries, even though people learned much about the disease and how it spreads during the London epidemic of 1846?

Largest delta in the world. kidhar hai market mein india

When studying the calumet region of illinois and indiana alfred meyers noted four stages of development as new groups occupied this land in stage 2 farmers used the land primarily to grow food for their familes and their small communities

What would be the distance of all the planets to the sun in astronomical units?