Passage
Tardigrades, microscopic eight-legged animals often called water bears, are famous for their ability to survive in environments that would instantly kill almost any other form of life. When faced with extreme conditions, such as freezing temperatures, intense radiation, or the vacuum of space, they enter a state called cryptobiosis. During cryptobiosis, tardigrades expel up to 99 percent of the water from their bodies, coil their heads and legs inward to form a tiny, dry sphere known as a "tun," and suspend their metabolic activity to near-zero levels. They can remain in this state for decades, only to revive within hours when rehydrated. Historically, scientists viewed life as a continuous chemical process. However, the tardigrade’s ability to completely pause its metabolism and successfully restart it suggests that life does not require active chemical reactions to persist. Instead, life can exist as a structural blueprint that can be temporarily deactivated and preserved. Thus, tardigrades do not merely showcase extreme adaptation; they fundamentally challenge biological definitions of what it means to be alive.
Which statement best summarizes the author's primary argument in the passage?
- ATardigrades protect themselves from extreme conditions by expelling most of their body water and coiling into a protective sphere called a tun.
- The tardigrade's ability to suspend and restart its metabolism forces scientists to reconsider the fundamental definition of life.Answer
- CMicroscopic organisms possess diverse biological mechanisms that allow them to adapt to any environment in the universe.
- DTardigrades are the only organisms that can survive extreme radiation and the vacuum of space without experiencing cellular damage.