What does the word "contaminated" (Sentence 9, Para.2) mean

A．a way of farming that is completely free of chemicals
B．a kind of food from which all chemicals have been removed
C．a way of growing things without using artificial chemicals
D．a kind of food that contains natural but not artificial chemicals

A．They knew organic produce was in demand.
B．They wanted to grow their own food.
C．They had been trained in organic farming.
D．They had moved together to the country.