A Researcher Has Several N

A researcher has several N. attenuata plants growing in a field. He encloses one of these plants in an "airtight" and "sound-tight" plastic container, into which he constantly pumps air from a nearby canister. He then introduces M. sexta caterpillars into this container and assesses the expression of defensive compounds in the neighboring (nonenclosed) N. attenuata plants. What will he find?

A) Given that N. attenuata plants produce signals that travel through the soil, the plants surrounding the individual harboring M. sexta caterpillars will demonstrate an increase in defensive compounds.
B) Given that N. attenuata plants produce signals that travel through the air (and the plant with the caterpillars is in an isolated, air- (and sound-) tight container) , the plants surrounding the individual with the caterpillars will not demonstrate an increase in defensive compounds.
C) Given that N. attenuata plants produce signals that travel through common water sources, the plants surrounding the individual harboring M. sexta caterpillars will demonstrate an increase in defensive compounds.
D) Plants only express defensive compounds if they themselves are actively preyed upon; plants will never increase their production of defensive compounds if only a neighboring plant is being eaten.