The community knew the effects of Chemical X and Chemical Y when used independently of one another.Safe limits were set for the use of each chemical.When both chemicals were released into the environment at their safe levels,but at the same time and location,massive quantities of fish died.What is the most probable explanation for this occurrence? 

A)  negative feedback 
B)  synergistic interaction 
C)  positive feedback 
D)  homeostasis

When two chemicals interact in a way that their combined effect is greater than the sum of their individual effects, it is called a synergistic interaction. In this case, it is possible that Chemical X and Chemical Y, when combined, exceeded the safe limits set for each chemical individually, leading to the massive fish die-off. This is a form of synergistic interaction. Negative feedback is a mechanism to maintain stability in a system, positive feedback amplifies change, and homeostasis refers to the ability of an organism to maintain a stable internal environment.