What is a ruler like symbol used to measure distance on a map?

How would i answer this for an exam?

All of the following came out of china and were exchanged along the silk road, except a. papermaking b. block printing c. buddhism d. compasses select the best answer from the choices provided a b c d

Plzz on what physical process is responsible for the creation of volcanoes, earthquakes and ocean trenches at the plate margins?