Fill in the blanks:
$(a)$ $A$ total of . . . . . . nutrients are essential to plants.
$(b)$ . . . . . . and . . . . . . are supplied by air to plants.
$(c)$ . . . . . . is supplied by water to plants.
$(d)$ Soil supplies . . . . . . nutrients to plants.
$(e)$ . . . . . . nutrients are required in large quantities and are called . . . . . . .
$(f)$ . . . . . . nutrients are needed in small quantities for plants and are called . . . . . . .

What are the advantages of intercropping?

Identify two crops from the following which provide us carbohydrates for energy requirement:
Black gram,Wheat,Lentil,Rice

Sid went to market to buy foodgrains for his home and on returning when his mother found the grains discoloured and of low and poor quality,she returned them back to the vendor. The vendor told Sid's mother that it was due to the storage loss of the grains that resulted in their poor quality and gave her the good quality grains.
$(a)$ What kind of qualities are shown by Sid's mother?
$(b)$ What could be the control measures to prevent this storage loss?

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?

The number of dengue cases has increased in Sana's village in the last one year. She read in her textbook that diseases like dengue spread through mosquitoes which breed in stagnant water. She immediately suggested to her friends that they should kill the mosquitoes in water bodies in the locality. They also took the help of the nearest municipal office.
$(a)$ Which preventive measures do you suggest for the prevention of such diseases caused by mosquitoes? Mention any two measures.
$(b)$ Which values are displayed by Sana in taking this initiative?
$(c)$ Suggest one school activity to promote such values in school students.