Reading Comprehension

Read the passage and answer the question.

Tardigrades, often called water bears, are microscopic animals famous for surviving conditions that would kill almost any other creature. When their environment dries out, they curl into a dormant state, expelling most of the water from their bodies and nearly halting their metabolism. In this form they can endure extreme heat, freezing cold, intense radiation, and even the vacuum of space. Once water returns, they slowly revive and resume normal activity. Scientists study these remarkable survivors partly in the hope of learning how to preserve delicate biological materials, such as medicines, without refrigeration.