Sudan seizes the in$-$country copper mining assets of Huntsman Minerals, a U$.$S$.$ firm, based on the Sudanese government's policy to regain control of its natural resources. Huntsman's attempt to sue the Sudan government in a U$.$S$.$ court to enjoin this 'nationalization' may be blocked by application of

a$.$ the Act of State Doctrine.

b$.$ the Doctrine of Sovereign Immunity

c$.$ both a$.$ and b$.$ above

d$.$ the Foreign Corrupt Practices Act.