Final answer:
The correct sentence is 'They sell fruits, vegetables, and other delicious things at the market.' 'At' is the appropriate preposition to indicate the selling activity's location at the market.
Step-by-step explanation:
The correct answer to the question is C: They sell fruits, vegetables, and other delicious things at the market. This sentence expresses where the selling activity takes place, using 'at' to indicate the location of the market.
Option A uses 'on the market,' which could imply that the products are available for trade or investment, not typical for fruits and vegetables. Option B uses 'in the market,' which can also be correct but is less common in this context. Option D, 'for the market,' suggests that the items are being sold for the benefit or purpose of the market itself rather than to the people who shop there.
Using the preposition 'at' indicates the physical location of the activity, which fits the context of a customer physically going to a market to purchase goods.