Astronomers Estimate That About 25 Million Meteors Strike the Earth's

Astronomers estimate that about 25 million meteors strike the Earth's atmosphere each day. How come we haven't run out of meteors in the long history of the Earth?

A) meteors come from dust from the Earth's surface that winds have blown high into the atmosphere; the Earth is so big it has lots of dust
B) meteors are pieces of dirt left over from the formation of our solar system and from old comets; there is a huge supply of small dirt particles from both sources
C) meteors are caused by electrical sparking in the Earth's atmosphere and there is a lot of static electricity up there
D) meteors have only been hitting the Earth's atmosphere recently; they are the result of human pollution of space
E) this is an unsolved problem in astronomy that has a lot of astronomers mystified