The evidence that supports the classification of sponges as animals rather than plants is that sponges cannot make their own food. This characteristic aligns with the definition of animals, which are heterotrophic organisms that obtain their nutrients by consuming other organisms. In contrast, plants are autotrophic and can produce their own food through photosynthesis. While the lack of tissues or organs is also a distinguishing feature, it is the inability to produce their own food that more clearly categorizes sponges as animals. So, the correct answer is:
Sponges cannot make their own food.