The level of vitamins $A$ and $K$ is kept high in poultry feeds.

What are the merits and demerits of fish culture?

Sameer once went to his granny's home with his family and he saw his granny serving water from an earthen pot and was surprised to see that and asked granny why she has kept that earthen pot for storing water. His granny then answered him that it keeps the water cool during summers,he then smiled and thanked her.
$(a)$ According to you,how does water kept in an earthen pot become cool during summers?
$(b)$ What kind of qualities are shown by Sameer?

Ram tried hard to push the wall of a room. In the process of pushing the wall,he begins to perspire and feels exhausted although the wall does not move. Ram feels that he has done a lot of work and spent a lot of energy. Do you think that Ram was justified in making the statement that he has done a lot of work? Justify your answer and give the conditions under which work is done.

Chemical formula of a compound is a symbolic representation of its composition. We should know the following points to write the chemical formulae of chemical compounds:
$(i)$ Symbols of the combining elements.
$(ii)$ Valency of the combining elements.
In order to know the valency,we must calculate the valence electrons present in the atoms.
The electrons present in the outermost shell or valence shell are called valence electrons. The number of electrons in the atoms of some elements are given below. The elements which have one valency are called monovalent.
$(a)$ What is a chemical formula?
$(b)$ Which main points we must know to write the chemical formula of compounds?
$(c)$ Which values do we find associated with the use of formula for various things in daily life?

How do biotic and abiotic factors in stored grains lead to poor marketability? How can these factors be controlled?