以lack of gases and ices做关键词定位至倒数第二句，这句话只是单纯说现象，最后一句才是解释，而且这句话刚才已经讲过，说由于距离太阳近，类地行星最终失去了这些气态物质，所以答案是A。其余答案均与本段首句说反。
选项B对应第二段的第二句:“Pluto is not included in either category, because its great distance from Earth and its small size make this planet's true nature a mystery.”(冥王星不属于这两类中的任何一个,因为它距地球很远且体积较小,所以目前冥王星的真实形态仍然是个谜。)因此这个选项为干扰选项。
major planet,planet- (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellati...
in order to qualify as a planet. This means that a planet cannot have other objects in or crossing its orbit except smaller objects that have been captured by its gravity, such as those that revolve around it as moons. Because Neptune's large mass has captured Pluto so that the two ...
it might require the other known dwarf planets – Ceres in the asteroid belt; and Haumea, Makemake and Eris, all in the Kuiper belt beyond Pluto – to be considered planets as well. This would necessitate a new mnemonic, one with 12 words instead of eight. One pithy suggestion offered by...
Saturn, would actually float inwater. Each of the outer planets has a magnetic field, aring system, and many known moons, with more likely to be discovered. Pluto has no known rings and only five known moons. Several other Kuiper belt objects and some asteroids also have moons of their ow...
Planets in Our Solar SystemLook at the four squares [] that indicate where the following sentence could be added to the passage.如果对题目有疑问，欢迎来提出你的问题，热心的小伙伴会帮你解答。
Read the full-text online article and more details about "With Pluto out, Here's How to Remember Remaining Planets" by DeFiglio, Pam - Daily Herald (Arlington Heights, IL), September 19, 2006By DeFiglio
Many professionals in the field also criticize the IAU definition of trying to limit the number of planets with the most recent change to the definition, as it was ultimately responsible for Pluto being removed as the ninth planet and re-labeled a dwarf planet. ...
The eight planets that orbit the sun are (in order from the sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Another large body is Pluto, now classified as a dwarf planet or plutoid. A belt of asteroids (minor planets made of rock and metal) lies between Mars and...