What Is the Main Difference Between Plant Defense Mechanisms That

What is the main difference between plant defense mechanisms that use secondary chemical metabolites versus plant defense mechanisms that use a systemic response?

A) The metabolites are not as lethal as the systemic response.
B) The metabolites are present at all times,and the systemic response must be induced.
C) The metabolites can only help in defense against insects,not against other plants.
D) The metabolites are toxic to the plants that produce them,the systemic response is safer.
E) The metabolites are a more reliable way to kill the invader.