The answer is the option a. Filter feeders - strain food from water. You can realize the the option b is no rirght because carnivores eat meat (other aninals), c is not rigth because paraistes do not help other animals but they harm other animals, and d. is not right because herbivores eat plants and not bits of decaying matter. So you can eliminate b, c, and d. While a. reflects exactly what filter feeders eat.
