Which of the following best expresses the essential information in the hightlighted sentence in the passage? Even today the barter system tends to come back into s...

A People still use barter because of poor social conditions or as an extra, unofficial activity

B The barter system sometimes reappears as a sideline activity in places experiencing social disturbances

C The barter system is used only informally in harmonious places, but as the main form of economic activity in troubled lands

D Bartering has always been common in both times of trouble and times of peace.