What Is the Relevance of the Court of Appeal's Decision

What is the relevance of the Court of Appeal's decision in Williams v. Roffey Bros (1991) for the doctrine of consideration?

A) It established that consideration is not necessary for contract modifications.
B) It established that consideration is not necessary where the parties have laid down their agreement in writing.
C) It established that consideration can consist not only of legal benefit or detriment, but also of 'practical benefit'.
D) It established that promissory estoppel can be used to enforce contract modifications.