Read the following snippet and answer the question that follows:
Most Europeans live in small villages. They grow their own food and barter with others. As well as keeping animals, they grow small crops of wheat, rye and vegetables. Milk, from dairy cows, is the vital part of the diet. This milk is also used to make butter and cheese.
Which of the following words can replace the word 'barter' used above, without changing the meaning of the text?