Help me please:( i need to choose the correct verb.

3. No one in Europe (was, were) familiar with the taste of pumpkins,
blueberries, or maple syrup until explorers brought these foods
back from the Americas.
4. One American food that helped reduce the famine in Europe
(was, were) potatoes.
5. A field of potatoes (produce, produces) almost twice as much food
in about half as much growing time as the same field would if it
were planted with wheat.
6. News of tomatoes, sweet peppers, beans, and zucchini (was, were)
received warmly in Europe, and now these foods are the heart and
soul of southern Italian cooking,
7. At our school the Original American Chefs (is, are) a club that
prepares and serves such American Indian foods as baked sweet
potatoes and steamed corn pudding.