In which of the following cases is the economy most likely considered a hyperinflationary economy?

a An economy that has a cumulative inflation rate of 90% over a three-year period

b An economy in which the annual inflation rate increased by half when compared to the prior year

c An econmy in which the annual inflation rate doubled when compared to the prior year

d An economy that has a cumulative inflation rate approaching or exceeding 100% over a three-year period