If the United States Unilaterally Removed All of Its Trade

If the United States unilaterally removed all of its trade restrictions and moved toward a policy of free trade, international trade theory indicates that

A) U.S. residents would gain, but people in other countries would be worse off.
B) people in other countries would gain, but U.S. residents would be worse off.
C) both U.S. residents and people in other countries would be able to achieve higher income levels.
D) the average income level would be lower in both the United States and other countries.