To obtain new computers, Liberia accepts bids from U.S. firms, including Macro Corporation and Micro, Inc. Macro wins the contract. Alleging impropriety, Micro files a suit in a U.S. court against Liberia and Macro. The court may decline to hear the suit under

a. the act of state doctrine.

b. the doctrine of sovereign immunity.

c. the principle of comity.

d. the World Trade Organization.