ACT

Practice session

Read the following passage and answer the question. "Although Pluto was discovered in 1930 and considered a planet for 76 years, the International Astronomical Union (IAU) reclassified it as a 'dwarf planet' in 2006. The IAU's new definition required a planet to (1) orbit the Sun, (2) have sufficient mass for gravity to make it roughly spherical, and (3) have 'cleared the neighborhood' around its orbit of other debris. Pluto meets the first two criteria but fails the third — it shares its orbital zone with many other Kuiper Belt objects." Why was Pluto reclassified as a dwarf planet according to the passage? A) It was found to be too small to orbit the Sun. B) It failed to clear its orbital neighborhood of other debris. C) It was not sufficiently spherical in shape. D) The IAU determined it was not actually orbiting the Sun.

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