An economist remarks,

$"$In the $1960$ s$,$ fiscal policy would have been a better way to stabilize the economy, but now I believe that monetary policy is better."

What has changed about the U$.$S$.$ economy that might have led the economist to this conclusion?

A$.$ The economy is more open today than it was in the $1960$ s$.$

B$.$ There is more government regulation today than there was in the $1960$ s$.$

C$.$ Monetary policy had more of an impact on aggregate demand in the $1960$ s than it does today.

D$.$ There are more tariffs and trade barriers today than there were in the $1960$ s$.$