A. Ammonium = polyatomic ion
B. Oxygen = compound
C. Silver = element
D. Nitrate = polyatomic ion
E. Helium = element
F. Water = polyatomic ion
G. Nitrogen = element
H. Carbon dioxide = compound
A. Mutualism. This is because both the larvae and the flower are benefited. The larvae is fed, and the flower is pollinated.
Hope this helps!
Magnesium in hydrochloric acid forms H2 (hydrogen) gas according to the balanced chemical equation:
Mg + 2HCl→H2 + MgCl2