Which defence compound of the cassava root becomes toxic only after a herbivore eats it?

1. Secondary metabolites are compounds not directly derived from photosynthesis and not needed for respiration or growth. 2. Many are toxic and some become toxic only after ingestion. 3. Glycol cyanide in the cassava root releases cyanide only when a herbivore eats it. 4. Quinine works instead through a repellent bitter taste and needs no conversion. 5. Caffeine acts by excessive stimulation of the herbivore, again without waiting for ingestion to activate it. 6. Volatile oils such as those of mint and sage discourage predators by odour before any feeding occurs. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.6 Plant Sensory Systems and Responses_