The line that separates the crust from the mantle is called the

Hey! 
Its called the Moho! 
Hope this helps! 
Godspeed 
-Song

Historians are researchers of the past or people who understand the history of people. with this field, they must possess qualities such as being unbiased, patient, efficient reader, has a knack for logic and critical thinking and reasoning, disciplined, open-minded, resourceful, with good analytical ability, good reasoning skills and problem solving!

2pi more meters because you find the circumference which is 6pi and 4pi and subtract it and you get 2pi