A Financial Bubble Starts to Inflate When

A financial bubble starts to inflate when:

A) investors become irrationally optimistic that an asset's price will continue to rise.
B) investors become irrationally pessimistic that an asset needs to be sold immediately.
C) a good experiences a rise in demand that is unexplained,increasing its price.
D) inflation begins to accelerate,and monetary and fiscal policy are ineffective at slowing its growth.