Chris, the Owner of Bloom's Aglow, Offers to Contract with Lisa

Chris, the owner of Bloom's Aglow, offers to contract with Lisa for her upcoming wedding bouquet and decoration needs. Chris specifically states in the offer that he will only use the Western Prairie Fringed Orchids in all arrangements. While contemplating the offer, the federal government passes a law that classifies the Western Prairie Fringed Orchids as a near extinct flower and makes it illegal to use, to sell or to kill it. Does this affect the offer between Chris and Lisa?

A) No because the offer was made before the law changed, Lisa has the option to accept and create a contract as is.
B) No since the law would affect people for previous conduct, it is an ex post facto which is unconstitutional and therefore unenforceable.
C) Yes because the change in law constitutes a supervening illegality and therefore, the offer is revoked.
D) Yes because forcing someone to commit a crime to avoid a breach of contract is collusion and unenforceable.