After the President Signs a Piece of Legislation into Law

After the president signs a piece of legislation into law, why do interest groups not stop working with the executive branch?

A) More often than not, loyalty to the president's party is involved.
B) The friendships developed with executive branch members lead to subsequent get-togethers.
C) Groups typically fear that there might be attempts to undo the legislation in Congress.
D) Faithful implementation of the law is not guaranteed and requires continued contact.