11.The word “extensive” in the passage is closet in meaning to A.developing B.large C.complex D.centralized 阅读原文中文译文 The orderly nature of our solar system leads most astronomers to conclude that the planets formed at essentially the same time and from the same primordial (original)...
they're basically made up of debris left over from the origin of the solar system 4.6 billion years ago.Now I'm going a bit out of order here, um,I’m not going to go into any depth on uh comets and asteroids now, but we'll come back later and do that.For now I'll just cov...
Professor: Exactly. In fact, it's almost a certainty.We know that there were lots of meters in our region of the solar system during this time period.And quite a few of them hit the earth with a big enough impact, tons of earth rocks would have been tossed up into space.So it's ...