DDT was used during second world war to control malaria among the troops and the civilians. Later, it was used as pesticide in agricultural and household practices. Due to its excessive use it entered into the food chain and its amount in the food crossed the permissible level. So, it was banned by United States.
Answer:
This method is used for separating bran from flour, sand from gravel, pearls of different sizes, etc. Winnowing:The process of separation of lighter particles from heavier particles; with the help of wind; is called winnowing. This method is also used for separating grains from husk.
