$A$ farmer wanted to invest some money in fish farming. But he did not get right guidance.
$(a)$ How can you guide him for a profitable business in spite of limitations of fish farming?
$(b)$ What is the limitation of fish farming?

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?

Why is there a need for varietal improvement?

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?

Bhetki,mullets,pearl spots and prawns are some of marine fish of high economic value.

Jessica saw her mother rotating a milk churner in a container of milk. She was surprised and asked her mother why she was doing that. Her mother smiled and explained that she was separating cream from milk,which would be used in various dishes.
$(a)$ What kind of qualities are shown by Jessica's mother?
$(b)$ How is cream easily separated from milk by a milk churner?