A) is the correct answer. Perihelion is the point in a planet's orbit where it is closest to the Sun. Since the Earth orbits the Sun, perihelion is the point where the Earth is nearest to the Sun. This has important effects on the seasons and climate on Earth. The other answer choices are incorrect because: B) refers to the alignment of the Sun, Moon, and Earth, which is not the definition of perihelion. C) is the opposite of perihelion, which is the farthest point from the Sun. D) describes the position of the Earth relative to the Moon, not the Sun.