The butterfly is busy sucking nectar.

The correct answer is option 'A' - sucking nectar. Butterflies have a unique and specialized feeding behavior. They primarily feed on nectar, which is a sweet, sugary liquid produced by flowers. Nectar is a rich source of energy for the butterfly, providing it with the necessary nutrients to survive and reproduce.

Butterfly feeding process:
- Sucking nectar: Butterflies have a long tube-like structure called a proboscis, which acts as a straw for sucking up nectar. When a butterfly lands on a flower, it extends its proboscis and inserts it into the flower's nectar-producing part, such as the base of the petals or the center of the flower.
- Drinking nectar: Once the proboscis is inserted, the butterfly begins to drink the nectar by drawing it up through the tube. The nectar flows into the butterfly's digestive system, providing it with a quick source of energy.
- Benefits of nectar: Nectar is not only a food source for butterflies but also serves as a means of pollination for the flowers. As butterflies move from flower to flower in search of nectar, they inadvertently transfer pollen from one flower to another, aiding in the fertilization process and ensuring the production of seeds and fruits.

Butterfly and flower relationship:
- Attracted to flowers: Butterflies are attracted to flowers by their vibrant colors, sweet scents, and the presence of nectar. They have developed a close relationship with flowers, as both parties benefit from this interaction.
- Co-evolution: Flowers have evolved specific characteristics to attract butterflies, such as bright colors and intricate patterns that act as visual cues. They also produce nectar in specific locations to guide the butterfly's proboscis to the reproductive parts of the flower, increasing the likelihood of pollination.
- Butterfly as pollinators: Butterflies play a crucial role as pollinators in many ecosystems. By visiting different flowers for nectar, they inadvertently transfer pollen from one flower to another, facilitating cross-pollination and maintaining genetic diversity within plant populations.

In conclusion, butterflies are busy sucking nectar from flowers as part of their feeding behavior. This activity not only provides them with the necessary nutrients for survival but also contributes to the pollination process, benefiting both the butterflies and the flowers they visit.