The correct answer is A. The sun is much closer to Earth than other stars are.
Step-by-step explanation
According to the fragment, a student does not understand why other stars larger than the sun look smaller than him when seen through a telescope. This situation is because the sun is 0.00001581 light-years from Earth while other stars larger than the sun are much further from Earth such as the star Betelgeuse, which is about 500 light-years from Earth. So the correct answer is A. The sun is much closer to Earth than other stars are.