I believe the answer is D. polar;subtropical.
In the Northern Hemisphere, the<u><em> polar </em></u>jet stream brings cold weather conditions from the north, and the<u><em> subtropical </em></u><em />jet stream brings warm weather conditions from the south.
I hope this helped!
I think it would be cold front ^^, I hope it helps!
Fruit flies share 75% of the genes that cause diseases with humans, so scientists can learn about human genetics by studying fruit fly genetics.