What is the significance of greenwhich England

the answer is The line in Greenwich represents the historic Prime Meridian of the World - Longitude 0º. Every place on Earth was measured in terms of its distance east or west from this line. The line itself divided the eastern and western hemispheres of the Earth - just as the Equator divides the northern and southern hemispheres.

Explanation:

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.