What is an example of a positive external shock?

Most civilizations require payment to government in form of a tax. a tax is a payment to the government for protection, celebrations, buildings, and many other things that benefit the people. the sixteen to eighteen million people in the aztec empire had to pay such taxes to their leader, montezuma. what payment might they have they been most unhappy with? a the required payment of corn to feed the emperor, his servants, and to feed the people at times of celebration and in times of need. b the required payment of silver to trade with other empires. c the required payment of their sons and daughters to be kept as slaves or sacrificed to the gods. d the required payment of gold to the emperor for fancy jewelry.