The answer is hydroiodic acid.
Answer: Atmosphere
Explanation:
if a scientist wants to predict the weather, they should most directly study Atmosphere.
Carbon is more electronegative
It is D because nitrate reacts with the calcium and since na has a 2+ charge and no3 has a - charge we need 2 no3 to balance out the charge hence a 2 is placed outside the no3 bracket.