Which aspect of herbicide tolerant crops is true?

Herbicide tolerant crops can indeed be developed through both conventional breeding methods and biotechnology, making this statement true. Conventional breeding techniques have been used for decades to select for natural variations that exhibit herbicide tolerance. In contrast, biotechnology involves introducing specific genes into the plants to confer this ability more rapidly and precisely. This versatility in development means that herbicide tolerance is not limited to genetically engineered crops alone, allowing for a broader range of cultivation practices.

The other statements about herbicide tolerant crops do not hold true in the same manner. While many of these crops are genetically engineered, it's not accurate to say that all of them are – as mentioned, conventional breeding also plays a role. The assertion that they provide complete pest resistance is misleading, as herbicide tolerance specifically addresses plant response to herbicides rather than providing broad-spectrum resistance to all pests. Lastly, the notion that these crops always require a high dose of chemicals is incorrect; the effectiveness of herbicides can vary and not all herbicide applications necessitate high doses to achieve the desired control.