Invasive species constitute a serious threat to (I) ________ plants and animals, whether by preying on them directly or competing with them for resources. The emerald ash borer has had a particularly (ii) ________effect on the environment; as its name implies, it attacks and kills all varieties of ash trees, and it is spreading throughout the United States at an alarming rate.

Blank (i)	Blank (ii)
A. inveterate	D. deleterious
B. pugnacious	E.covert
C. indigenous	F. perfidious