The answer is C, West Nile virus!
Well, I don't fully understand your question. I think I know what you're getting at though.
In a system of sexual reproduction, you have genes coming from both an egg and the sperm. Therefore, it'll only contain half the total amount of chromosomes (46 in humans). A sperm will have 23, and the egg will have the other 23. Is that what you meant why the chromosomes are cut out in pairs? If that wasn't your question, please elaborate and I'll return to answer it to the best of my capabilities.
High air pressure cuz low pressure brings da rain and everybody is sad
The part anti means opposed. Biotic is basically all the naturally occurring organisms. So an antibiotic would oppose an organism like a virus.
Can overload the immune system, causing you to become sick, and open to sicknesses.