According to your lesson, what is the origin of christianity

What is a compass? how does it work

The blue segment below is a diameter of oo. what is the length of the radius of the circle?

This is a 2017 topographic map of puerto rico in the united states, and i'm sorry that people there have suffered such a disaster. i want to ask, what do the yellow dots and areas represent on this graph? and the blue area and the little blue circle, and the little blue sign that looks like a signal tower, what do they stand for?