Hint: A flower is the reproductive part of a plant found in angiosperms which are considered as a shoot bearing nodes and modified floral leaves. A flower is borne at the mother axis and it attracts several agents by its nectar and color for pollination.
The gynoecium is the innermost whorl consisting of female reproductive organ carpels and the unit of gynoecium is called a pistil. A pistil is divided into a basal swollen ovary, stalk-like style, and terminal part stigma. An ovary may be unilocular, bilocular, trilocular, and tetralocular depending upon the number of chambers in the ovary. Oval outgrowth present in the ovary is known as the ovule. A style is a narrow, thin structure used to raise the level of stigma above the ovary. Stigma is the upper part of the pistil which acts as a receptor of pollen. It is feathery, hairy, and sticky.
Stamen is the male reproductive organ present in androecium. A highly modified stamen is called microsporophyll. A stamen consists of a slender stalk filament and knob-like structure anther. Generally, anther is divided into two-lobes therefore considered as bilobed anther. Each lobe consists of two pollen sacs or microsporangia which consist of a large number of pollen grains. The stamens that are borne on the thalamus on fusion with petals are epipetalous. Stamen alternate with petal is alternipetalous, opposite petal is antipetalous. The free stamen are polyandrous which may be equal or unequal in length. United stamens are cohesion and stamen shorter than corolla are inserted, and those who come out of corolla are expected.
So, the correct answer is option (b) ‘Pistil’.
Note: Some stamen and pistil do not take part in reproduction, that type of organ is called sterile. Sterile and undeveloped stamen is staminodes while sterile and undeveloped pistil is pistillode. Sterile reproductive organs are mainly found in hybrid plants which are due to improper fertilization.