The Addition of Either the Methyl Grignard Reagent or Methyllithium

The addition of either the methyl Grignard reagent or methyllithium to camphor,followed by hydrolysis,produces a tertiary alcohol known as 2-methylisoborneol,an algal metabolite which imparts a musty odor to water at very low concentrations.However,the yield of alcohol does not exceed 50%,and large amounts of camphor are recovered from the reaction even when a large excess of the Grignard or lithium reagent are used.What would be the most plausible explanation?

A) Ketones do not react with Grignard or lithium reagents.
B) The Grignard or lithium reagent had obviously degraded during storage.
C) The mechanism requires that,for each alcohol formed,one ketone molecule must remain unreacted.
D) With hindered ketones,the organometallic reagent could function as a base rather than as a nucleophile.
E) Alcohol formed early in the reaction could form an unreactive hemiacetal with remaining ketone.