For what reasons are improved poultry breeds developed?

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?

The figure shows two crop fields [Plots $A$ and $B$] that have been treated with manures and chemical fertilizers,respectively,while keeping other environmental factors constant. Observe the graph and answer the following questions.
$(i)$ Why does plot $B$ show a sudden increase and then a gradual decrease in yield?
$(ii)$ Why is the highest peak in the plot $A$ graph slightly delayed?
$(iii)$ What is the reason for the different patterns of the two graphs?

Which one of the following fishes is a surface feeder?

"There is a need for sustainable practices in agriculture and animal husbandry". Mention the reason for their need.