A new planet-hunting technique has detected the most earth-like planet yet around a star other than our sun, raising hopes of finding a space rock that might support life, astronomers   reported recently. "This is an important discovery to answer the question 'Are we alone?'" said Michael Turner of the National Science Foundation. "The team has discovered the most earth-like planet yet, and more importantly, has proved the power of a new technique that is sensitive   to detecting planets that are fit for people to live on," Turner said in a statement. In the last decade, astronomers have detected more than 160 planets moving around stars outside our solar system. Most of these have been gas giant planets like Jupiter, which are unfit for life. But an international team has detected a cold planet about 5.5 times more massive than the earth -- still small enough to be considered earth-like -- moving around a star about 20,000 light years away, close to the center of the Milky Way. To find this new planet, the team used a technique called gravitational microlensing  . When a planet is circling the closest star, the planet's gravity can add its own signature to the light. This kind of light signature was observed on July 11 by a group of telescopes in a project known as OGLE, short for Optical Gravitational Lensing Experiment. "The main advantage of microlensing is the signals for low-mass planets: They're not weak signals. They're just rare," Bennett of the University of Notre Dame in Indiana said by telephone. "If there happens to be a straight line between a foreground star with its planet and the background source star, then you're able to detect that planet." The author's purpose in writing this passage is to   _  .
prove that scientists have a lot of difficulties in doing scientific research explain why this planet moves around a star like our sun teach the readers some basic knowledge about the universe tell people about a new technique that finds the most earth-like planet moving round another star
Question: A new planet-hunting technique has detected the most earth-like planet yet around a star other than our sun, raising hopes of finding a space rock that might support life, astronomers   reported recently. "This is an important discovery to answer the question 'Are we alone?'" said Michael Turner of the National Science Foundation. "The team has discovered the most earth-like planet yet, and more importantly, has proved the power of a new technique that is sensitive   to detecting planets that are fit for people to live on," Turner said in a statement. In the last decade, astronomers have detected more than 160 planets moving around stars outside our solar system. Most of these have been gas giant planets like Jupiter, which are unfit for life. But an international team has detected a cold planet about 5.5 times more massive than the earth -- still small enough to be considered earth-like -- moving around a star about 20,000 light years away, close to the center of the Milky Way. To find this new planet, the team used a technique called gravitational microlensing  . When a planet is circling the closest star, the planet's gravity can add its own signature to the light. This kind of light signature was observed on July 11 by a group of telescopes in a project known as OGLE, short for Optical Gravitational Lensing Experiment. "The main advantage of microlensing is the signals for low-mass planets: They're not weak signals. They're just rare," Bennett of the University of Notre Dame in Indiana said by telephone. "If there happens to be a straight line between a foreground star with its planet and the background source star, then you're able to detect that planet." The author's purpose in writing this passage is to   _  .
A. prove that scientists have a lot of difficulties in doing scientific research
B. explain why this planet moves around a star like our sun
C. teach the readers some basic knowledge about the universe
D. tell people about a new technique that finds the most earth-like planet moving round another star
Answer: