The bee carries the pollen back to its colony on:

The correct option is "Its rear legs".

Bees have specialized structures specifically evolved for collecting and transporting pollen back to their hives or colonies. These structures, known as pollen baskets or corbiculae, are located on the tibia of their hind legs (rear legs).
As a bee visits flowers, pollen grains stick to the hairs on its body. The bee then uses its legs to groom its body, brushing the pollen into the pollen baskets on its rear legs, where it is packed tightly for transport back to the colony.