Which one of the following is not used in organic farming?
Snails are garden pests, which mostly eat old rotting plants, plant seedlings, leafy vegetables and fruits that grow at ground level. The parts of the plants eaten by snails usually have a ragged hole look. Glomus, earthworm and Oscillatoria are used in organic farming either as a biofertilizer or to improve the quality of the compost. Snails are not used in organic farming.
Therefore, the correct answer is option A.