When Billy’s upstairs neighbor wakes up early to take a shower, Billy is typically awakened when the water starts, but then he gets used to the noise and goes back to sleep. In this example, Billy is showing learning through:.a. sensitization. b. conditioning. c. modeling. d. habituation.

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.

the answer to your question is,

old stone age.

-mabel < 3