A、It has the identical inner structure to Earth. B、It has a mass of four to six times that of Earth. C、It takes 73 days to orbit

Astronomers have discovered a potentially habitable planet of similar size to Earth in orbit around a nearby star. A team of planet hunters spotted the alien world circling a red dwarf star called Gliese 581, 20 light years away. The planet is in the "Goldilocks zone" of space around a star where surface temperatures are neither too hot nor too cold for liquid water to form. If confirmed, the planet would be the most Earth-like that has ever been discovered in another solar system and the first strong contender for a habitable one. More than 400 exoplanets have been discovered by astronomers, but most are gas giants, like Jupiter, that would be inhospitable to life as we know it. Astronomers used the Keck telescope in Hawaii to study the movement of Gliese 581 in exquisite detail and from their observations inferred the presence of a number of orbiting planets. The team report two new planets in the Astrophysical Journal, bringing the total number known to be circling the star to six. One of the planets, named Gliese 58lg, has a mass of three to four times that of Earth and takes 37 days to orbit the star. Astronomers believe it is a rocky planet with enough gravity to retain an atmosphere. Unlike the previously discovered planets, Gliese 58lg lies squarely in the region of space where life can thrive. One side of the planet is always facing the star, much as one side of the moon constantly faces Earth. The average temperature on the planet is estimated to be between -31 to -12℃, but the ground temperature would vary from blazing hot on the bright side and freezing on the dark side.
Questions 22 to 25 are based on the passage you have just heard.
22. What can we learn about Gliese 581?
23. How many planets are circling Gliese 581 so far as we know?
24. What do astronomers think of the planet Gliese 581g?
25. In what aspect does Gliese 581g resemble the moon?