Fill in the blanks:
$(a)$ Pigeon pea is a good source of . . . . . . .
$(b)$ Berseem is an important . . . . . . crop.
$(c)$ The crops which are grown in the rainy season are called . . . . . . crops.
$(d)$ . . . . . . are rich in vitamins.
$(e)$ . . . . . . crop grows in the winter season.

Which one is not a source of carbohydrate?

$(a)$ State three ways by which pests attack the plants.
$(b)$ Name the chemical used to control pests.
$(c)$ Explain why excessive use of such chemicals should be avoided.

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?

Weeds affect the crop plants by

Suggest some preventive measures for the diseases of poultry birds.