Read the passage and choose the best answer to each of the following questions.
For many years, scientists have been searching for life beyond Earth. The universe is unimaginably large, with billions of galaxies, each containing countless stars and planets. Some of these planets may have the right conditions for life, just like Earth. Scientists believe that in order for life to exist, a planet must have liquid water, a suitable temperature, and an atmosphere that can protect living things.
One of the most studied planets in our solar system is Mars. Scientists have sent many missions to explore the surface of Mars, searching for signs of past or present life. Mars has frozen water at its poles and evidence that liquid water once flowed on its surface. However, no living organisms have been discovered yet.
Beyond our solar system, astronomers have identified thousands of exoplanets - planets that orbit stars outside our solar system. Some of these exoplanets are in the “habitable zone,” the region around a star where conditions might be right for life. The most famous discovery is Proxima b, an exoplanet orbiting Proxima Centauri, the closest star to our solar system. Although it is in the habitable zone, scientists are still unsure if it has the necessary conditions for life.
To search for extraterrestrial life, scientists also study signals from space. The Search for Extraterrestrial Intelligence (SETI) is a project that listens for radio signals from distant planets. If intelligent life exists, it might try to communicate by sending signals into space. So far, no clear signals have been detected, but the search continues.
The question of whether we are alone in the universe remains unanswered. While no direct evidence of life beyond Earth has been found, scientists believe that with new technology and exploration, we may one day discover life on another planet.