About how often does a 1-kilometer object strike the earth? about how often does a 1-kilometer object strike the earth? every year every million years every billion years

The correct option is the second one, which is: Every million years.

 The impact of a 1-kilometer object on our planet, would cause significant consequences. As the astronomers have found in other terrestrial bodies, this kind of impact creates largers craters on the surface.

Wavelength divides in half and speed stays the same.