Answer: b. Asteroids can cause great damage if they collide with Earth.
Explanation:
The main idea is that asteroids can cause great damage to earth if they collide with our planet. This is what the entire article was centred around starting with an example of the effects of the last time there was a collision with Earth.
It then goes forward to talk about the chances of being hit by another asteroid and what scientists will do if the Earth is at risk of being hit by one which shows that the whole point of the article is the damage asteroids can cause on earth and why this should be avoided.
World War 2 occurred in the late 40's, so this is most likely why there is a dip in that age group.
It was Carl O. Sauer who did
-- One feature of Earth is an atmosphere rich in nitrogen and oxygen.
Very unusual.
-- Another feature of Earth is vast quantities of liquid and solid water.
Very unusual.
-- Another feature of Earth is a range of temperatures near the melting point
of water.
Very unusual.
