Question

If you have an altitude of 55 mi. (miles), which layer of the atmosphere are you in?

Answer 1

$Answer:$ $You$ $would$ $be$ $in$ $the$ $D-region$

$The$ $reason$ $I$ $understand$ $this$ $is$ $because$ $the$ $D-region$ $stands$ $55$ $miles$ $in$ $altitude$, $despite$ $it$ $will$ $likely$ $vanishes$ $at$ $night$.