"some european nations have experienced a debt crisis. what caused this crisis?

a.
the interest rate on bonds dropped so low during times of economic austerity that some nations could not earn enough interest on money they lent to investors.

b.
too many recent immigrants in some nations have drained these countries’ resources.

c.
during times of economic prosperity, some nations borrowed more money than they can pay back now in times of economic hardship.

d.
unscrupulous national leaders embezzled money from the treasuries of some european countries."