The beauty of Bougainvillea flowers is due to
A) Corolla
B) Calyx
C) Bracts
D) Androecium

Hint: They are a modified or specialized leaf, mainly one associated with a plant organ such as a flower, inflorescence axis, or cone scale. They’re often different from foliage leaves. They’ll be smaller, larger, or of a particular color, shape, or texture.

Complete answer:
The real flower of the Bougainvillea plant is small and typically white, but each bunch of three flowers is enclosed through three or six bracts with extreme colors (pink, magenta, purple, red, and orange). The sweetness of the flower is because of these bracts. Bougainvillea is additionally known as a paper flower as the bracts are thin and papery.

Additional Information:
Bougainvillea should be cultivated on higher ground or hillsides, not in water-logged or low areas where water might accumulate. They are going to grow best when provided sufficient space to open and can be planted during a neighborhood which can permit them a minimum of 5-6 hours of sunlight a day.
Some bracts are brightly-colored and provide the key to attracting pollinators, either in conjunction with the perianth or instead of it. Samples of this type of bract contain Christmas flowers (poinsettia) and Bougainvillea : both of these have huge colorful bracts enclosing much smaller, less colorful flowers. In grasses, every floret (flower) is surrounded while a combination of papery bracts, known as the lemma (lower bract) and palea (upper bract), while each spikelet (a group of florets) features a further pair of bracts at its bottom known as glumes. These bracts from the chaff are away from cereal grain while threshing and winnowing.
So, the correct answer is option (C) 'Bracts'.

Note: The sap of Bougainvillea could cause serious skin rashes. Some bracts are brightly-colored and give the function of attracting pollinators. Bracts that emerge during a whorl subtending an inflorescence are collectively known as an involucre.