When studying abroad, shelby talks about the racial categories in the united states. her new friends from other countries are surprised and say that racial categories based on expressed differences such as skin color are different in their countries. shelby remembers from her anthropology class that racial categories are determined by: ?

The answer is:

mental maps of reality

Shelby remembers from her anthropology class that racial categories are determined by mental maps of reality.

Mental maps of reality is a persons point-of-view perception of their area of interaction. We all have mental maps we carry around in our heads to make sense of the geographical world around us.

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals