With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Vegetable garden bed construction materials should be chosen carefully. Some concerns exist regarding the use of pressure-treated timber. Pine that was treated using chromated copper arsenate or CCA, a toxic chemical mix for preserving timber that may leach chemicals into the soil which in turn can be drawn up into the plants, is a concern for vegetable growers, where part or all of the plant is eaten. When timber is used to create the structure that holds up the garden bed, one should make sure to only use wood that has not been pressure treated, or else the chemicals in the wood could contaminate the soil. A common approach is to use timber sleepers joined with steel rods to hold them together. Another approach is to use concrete blocks, although less aesthetically pleasing, they are inexpensive to source and easy to use.
text_B: Would a backyard vegetable farmer need to find a way to prevent termites from entering the wood at ground level, since no completely-safe forms of treated lumber would be available to them?
YES.