What rule should be applied before a non-native species is introduced to an ecosystem or habitat? 

A)  the first law of thermodynamics 
B)  the law of common property 
C)  the law of supply and demand 
D)  the precautionary principle

Precautionary Principle

A strategy to cope with possible risks where scientific understanding is yet incomplete, favoring preventive action in the face of uncertainty.

Non-Native Species

Species that are brought into a new habitat where they do not naturally occur, potentially causing harm to the native species and ecosystems.

Ecosystem

A biological community of interacting organisms and their physical environment.