Teachers often ask this type of question when they are assessing how much students have learned from class activities and discussions. In these cases, teachers often have focused on specific imports and exports. For instance, sometimes teachers focus students on the imports and exports of their respective states. Generally speaking, however, the U.S. imports and exports everything from food, to medicines and medical supplies/equipment, to commercial goods (cars, clothing), to military goods. For a listing of exports and imports, the site I've included provides a wealth of information for you. Good luck on your search!