$$ extbf{Solution:}$$ $$ extbf{a)}$$ $$ullet$$ Diadelphous means united filaments of stamens clubbed together in 2 bundles. $$ullet$$ In pea flower, the stamens are united to form two bundles and therefore, the androecium is called diadelphous. $$ extbf{b)}$$ $$ullet$$ Neuters are non-fertile. It indicates absence of male and female reproductive organs. $$ullet$$ Ray florets of sunflower are neuters. $$ullet$$ They do not contain any male or female parts. $$ extbf{c)}$$ $$ullet$$ Petaloid means petal-like. $$ullet$$ In Salvia, the sepals are petaloid as 3 sepals are red in color and united as petals.  $$ullet$$ They are not differentiated from the petals.