Empirical Work Designed to Investigate How Well Imperfect-Information Theory Explains

Empirical work designed to investigate how well imperfect-information theory explains real world divergence between actual and potential GDP has shown

A) only that monetary changes precede employment and output fluctuations.
B) the importance of other types of shocks in macroeconomic fluctuations.
C) a strong correlation between price surprises and the GDP gap that provides impressive support for the theory.
D) a and b only.
E) none of the above because the data are so poor.