Bob has an unknown liquid and must determine what it is. he decides to systematically use a number of tests to determine the correct answer. what stage of cognitive development has bob reached?

answer: what do you mean

explanation:

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.