The organism described is multicellular, heterotrophic (eats other organisms), and capable of movement. Therefore, it most likely belongs to the animal kingdom.
The other options can be ruled out because:
- The protist kingdom primarily includes mostly unicellular organisms, although some multicellular forms exist, they typically do not share all the characteristics mentioned.
- The plant kingdom consists of primarily autotrophic organisms (those that produce their own food through photosynthesis) and do not move freely.
Thus, the best response is the animal kingdom.