"Excessive use of chemicals such as insecticides and pesticides causes a threat to ecology." Explain with reason.

Nakul was shooting his arrows towards a target. Every time the arrow fell short of the target. This annoyed him. His brother, Arjun, came to his rescue. He showed his brother the right way to shoot an arrow. When Nakul tried again, he found that the arrows started hitting the target.
$(a)$ What do you think Arjun might have told Nakul?
$(b)$ What are the values imbibed by Arjun?

List any three management practices while designing a shelter for cattle.

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?

Which one of the following nutrients is not available in fertilizers?

State how barseem,oats,or sudan grass are used by farmers.