سؤال اليوم — اختبار STEP

Read the passage and answer the question. (1) When people think of intelligent animals, they usually picture chimpanzees, dolphins or perhaps crows. Few would mention the octopus. Yet this soft-bodied relative of the snail has surprised scientists again and again with its ability to solve problems. (2) In laboratories, octopuses have learned to unscrew the lids of jars to reach the food inside, and some have found their way through simple mazes. In aquariums, they are known for their escape skills. Because they have no bones, they can squeeze through almost any gap larger than their beak, the only hard part of their body. Staff at several aquariums have reported octopuses leaving their tanks at night, apparently to visit nearby tanks in search of food. (3) The octopus's nervous system is very different from ours. It has around 500 million nerve cells, a number similar to that of a dog, but about two-thirds of these are found in its eight arms rather than in its brain. As a result, each arm can taste, touch and even make simple decisions on its own while the brain focuses on the bigger picture. (4) Octopuses are also masters of disguise. Special cells in their skin allow them to change color and pattern in less than a second, helping them to hide from predators or to surprise their prey. (5) What makes their intelligence especially puzzling is their short life. Most species live only one or two years, and mothers usually die soon after their eggs hatch, so young octopuses never learn from their parents. Scientists are still trying to understand why such a short-lived animal developed such a powerful mind. Question: The word "these" in paragraph 3 refers to