Iridium, a hard, whitish metal similar to platinum, is extremely rare on Earth. Extremely high
concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that
release iridium from deep within the Earth and meteorites that shower down on Earth from space.
When scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65
million years ago, they concluded that a massive meteor or comet hit the Earth and caused the massive
extinction of the dinosaurs.
嗯嗯 - - 你已经到了USA 了么?!~
我昨天问的一个美国那边的人,
他说A is more than 30 times B A>30B.
A is 30 times more than B A=30B.
后来又问了一个美国人,他说,that' s correct. = =
非常感谢你,you are so helpful~ ~