I think it's D because it is a response to stimulus
Answer: inertia
Explanation:
a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force
Z? ⠀ ⠀ ⠀ ⠀ ⠀ ⠀⠀ ⠀ ⠀ ⠀ ⠀ ⠀ ⠀ ⠀ ⠀ ⠀

The answer is that they treat bacterial infections.