How is spraying different from fumigation?

In winter, in the industrialised and metro cities, especially in the morning hours, the visibility is greatly lowered due to the formation of a dark fog, generally resulting in serious road accidents. It also causes suffocation.
$(a)$ What does this indicate and also name this phenomenon?
$(b)$ How is this phenomenon produced? Name two gases which cause acid rain.

Which one is not a source of carbohydrate?

$A$ farmer had a plot just beside the bank of a river. Each time he planted $Kharif$ crops,the crops got damaged due to floods. He consulted an agricultural scientist who gave him a special variety of seeds and also advised him to practice fish farming.
$(a)$ What was the specialty of these seed grains?
$(b)$ What name can be given to this type of fish farming?

"Different ways of growing crops can be used to give maximum benefit from crop production management." Explain any three techniques.

State two advantages of composite fish culture. What is the application of hormonal stimulation in fish culture?