The correct option is C monadelphous
Stamens are the male reproductive units in the flower. Stamen is comprised of anther that contains pollen grains and a thread like stalk called filament that attaches the the anther to the flower. Fusion of filaments of the androecium is called adelphy. If the stamens are arranged in a single bundle, it is called monadelphous, as in China rose. The stamens are arranged in bundles of two in the pea flowers and it is termed diadelphous.