For 22) Around 1000 Km is the best answer since 30 km is too small of an atmosphere...planes fly at 30,000 feet and that is above the troposphere and then we have to go to the stratosphere, mesosphere, thermosphere, and exosphere! 500 m is too small, too, only 0.5 km which does not even pass the troposphere! The ozone layer is at about 100 km, too, and still have the mesophere, thermosphere, etc. to go! 1 million meters is the same as 1000 Km. So, those two!