When there are no sidewalks, pedestrians should walk on the side of the road facing traffic.

It depends on what u r using

If this Oddysseyware, then put left because thats the right answer apparently

by using  production possibilities graph.  opportunity costs are key expenses in financial matters and are utilized as a part of registering money saving advantage investigation of a venture. such expenses, be that as it may, are not recorded in the record books but rather are perceived in basic leadership by processing the money costs and their subsequent benefit or misfortune.