The correct answer to complete the sentence is Option C.
The passage mainly speaks about GMO(Genetically Modified Organisms), and its effects if consumed by humans. While one section of the people say that genetic techniques are helping the food industry, the others, specially the food safety people, say otherwise.
Here in the latter part of the passage, the verbal fight between the two sections give clarity of what the definition of organic food is and better still, what it needs to contain. Thus, organic foods are described as being GMO-free, in the last sentence, as mentioned in Option C.
The other options A, B and D describe phrases which do not match the meaning of the term ‘organic foods’, rather are extensions to the same or qualities of them.