Aruler could lose the "mandate of heaven" if he or she
became immoral or unjust.
did not convert to buddhism.
did not pass the civil service exam.
were not the firstborn son or daughter.
answer- who knows

answer: a.became immoral or unjust

explanation:

the "mandate of heaven" is a chinese political and religious doctrine applying of the emperor of china, or how they used to call the ruler of china: the "son of heaven" of their "celestial empire". basically they believed that it was not required for a legitimate ruler to be of noble birth, but instead he would gain the right to rule based on the just and able performance of the rulers and their heirs, therefore if ever doing something immoral or unjust the ruler would lose the "mandate of heaven", the right to rule.

president jefferson protested this interference in american trade. he sent james monroe to london to negotiate a treaty. jefferson wanted britain to stop taking sailors from american ships, and to stop interfering in the trade of neutral nations. monroe tried many times to discuss such an agreement. but the british foreign minister was always too busy to see him.

explanation:

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.