Which of the Following Must Occur for a Plant to Initiate

Multiple Choice

Which of the following must occur for a plant to initiate chemical responses to herbivory, before it is directly affected by herbivores?

A) a plant must be old enough to have already flowered at least once
B) volatile "signal" compounds must be perceived from already attacked plants
C) gene-for-gene intraspecific recognition must occur between the plant and the herbivore
D) phytoalexins must be released by the herbivore