Hint: He was an Italian astronomer, physicist and engineer from Pisa. He is also called the father of observational astronomy, the father of modern physics and the father of modern science.
Complete answer: A. Galileo invented the telescope in 1609. B. He had heard that in the Netherlands an instrument had been invented that showed distant things. By trial and error, he was able to figure out the trick and made his invention of the telescope. C. He also figured out how to improve the instrument, and taught himself that art of lens grinding and he could make more powerful telescopes. D. By 1609 Galileo had started observing the sky with telescopes that magnified up to 20 times. He drew the moon's phases and discovered that the moon’s surface is not smooth as was previously thought. He also discovered four moons of Jupiter in 1610. His discoveries were absolutely earth-shattering.
Thus, the correct option is (A).
Note: In August 1609 Galileo presented his high powered telescope to the Venetian state, he was rewarded with a life tenure and a doubling of his salary. He became the highest-paid professor at his university.