Answer:
1. and 4.
Explanation:
For #1: Outside of a lab, different people's bodies may respond differently to the drug due to a one or many factors such as those listed in the response.
For #4: Pathogen mutations as well as bacterial growth and spread may render the drug incapable of curing the pathogen due to there simply being more bacteria in one person than the drug can handle.
The first step I would use is to use a magnet to remove the iron filings. This is because only metal is attracted to magnets. I would then use a sieve to filter the sand and salt from the gravel. This is because the gravel will have a larger diameter than the sand and salt particles, and will stay behind while the salt and sand will pass through the sieve. Finally, I would remove the salt from the sand by placing the mixture in water. The sand will tend to sink to the bottom while the salt will dissolve into solution.
Answer: Viruses are Zombie like because they go on stealth and are inactive outside the host.
