Answer:
acquisition
Step-by-step explanation:
Flatworms are worms that appeared on Earth probably about 600 million years ago. They live mainly in aquatic environments such as oceans, rivers and lakes; They are also found in humid terrestrial environments. Some live free, others parasitize diverse animals, especially vertebrates.
These worms are extremely sensitive to certain light intensities, writhing quickly when an incident light causes electric shocks on their bodies. The moment that flatworms contort the body in the face of a light with gradually increased intensity is called acquisition.