Reading Comprehension

Read the passage and answer the question.

Octopuses are remarkable for their ability to change color and texture in an instant. Their skin contains thousands of tiny cells called chromatophores, each holding a sac of pigment. By tightening or relaxing the muscles around these cells, an octopus can expand or shrink the colored sacs, shifting its appearance almost immediately. This skill serves several purposes. An octopus may blend into a rocky background to hide from predators, flash bright patterns to startle an attacker, or signal to other octopuses. Surprisingly, most octopuses are thought to be colorblind, yet they still match their surroundings with striking accuracy.