Fact 1: Apesticide is used for protecting plants by killing insects.

Fact 2: Plants are poisoned by herbicides, animals by pesticides.

Given the two facts above, answer the question "What doesn't protect plants?" with the following options: 
- viruses
 - smallpox
 - herbicide
 - steroids
 - A virus
 - Nematoda
 - chickenpox
 - cigarettes


 

   herbicide      