Answer:
At least 17 PCR cycles or 16 PCR cycles
Explanation:
As we know -
In one chain of heating and cooling of polymerase chain reaction (PCR), the strands of DNA gets doubled.
The general mathematical representation of this is

where "n" is the number of PCR cycles.
It is given that DNA strands to be produced is 16 times the original quantity of DNA.
So the PCR cycle must be carried out at least 17 times in order to have DNA strand not less than 16 times the original quantity of DNA
Answer: C) They can contain contaminants that can enter the air during storms or high winds.
Explanation: A is wrong because I got it wrong (Sorry, can't give much explanation there).
B is wrong because water contamination does not directly relate to respiratory health.
D is wrong because fertilizers can impact respiratory health (Explanation seems lack-luster, but I feel like this is common sense).
Hope this helps :)
I would say true. I say this because there have been times where scientists find out that there are better ways of performing experiments, or found that certain materials work better for certain tasks. (Especially true in medicinal fields!)