The united states highway system is a in the united states numbered within a nationwide grid.

Answer – System of roads
 The United States Numbered Highway System is an integrated system of roads in the contiguous United States numbered within a nationwide grid. This system of roads covers a total distance of 259,032 km. It is often called often called U.S. Routes or U.S. Highways

Ithink the answer to that would be b):

Answermost of the time it would be ground into fine sediment,and sometimes they are carried away from the original location;