The German hyperinflation of 1921-1923 provides important support for the view that high money growth causes high inflation because...

a.

The growth in the German money supply appears to have been due to exogenous forces.

b.

Reverse causation in this case is highly implausible.

c.

It is hard to imagine a third factor that could have been the driving force behind both inflation and explosion in the German money supply.

d.

All of the above.