The Slowest Step of an S_N1 Reaction Involves

The slowest step of an S_N1 reaction involves:

A) attack of the nucleophile on the substrate to form a pentavalent carbon.
B) breaking the bond between the carbon and the leaving group to give a carbocation.
C) combination of a nucleophile with the carbocation to give the product.
D) loss of a proton from the nucleophile to give the product.
E) none of the above.