Living organism interact with one another in their natural environment. The interaction of two organisms is called SYMBIOSIS. Symbiosis, however, can be of different types depending on how the organisms relate. One type of symbiotic relationship between organisms is called PREDATION.
Predation is a relationship between two organism in which one organism called PREDATOR kills and feeds on the other organism called PREY in order to obtain energy. In this question, a Manta Ray and a zooplankton is shown.
The Manta ray is described as an aquatic organism that feeds on tiny species like fishes while the zooplankton is a tiny organism found in water bodies. The Manta Ray is the predator that kills and feeds on the zooplankton, hence, the relationship is a PREDATION.
If you want to be precise, every measurement should include a tolerance, such as 15.5 +/- 0.1 cm. This way, when you do the calculations, you can figure out the uncertainty in the final result