The reaction is a decomposition…
![2KNO_3 \longrightarrow 2KNO_2 + O_2\\](https://tex.z-dn.net/?f=2KNO_3%20%5Clongrightarrow%202KNO_2%20%2B%20O_2%5C%5C)
… because one substance is forming two other substances.
![\text{2K}\stackrel{\hbox{+5}}{\hbox{N}} \stackrel{\hbox{-2}}{\hbox{ O}}_3 \longrightarrow \text{2K}\stackrel{\hbox{+3}}{\hbox{N}}\text{O}_2 + \stackrel{\hbox{0}}{\hbox{O}}_2\\](https://tex.z-dn.net/?f=%5Ctext%7B2K%7D%5Cstackrel%7B%5Chbox%7B%2B5%7D%7D%7B%5Chbox%7BN%7D%7D%20%5Cstackrel%7B%5Chbox%7B-2%7D%7D%7B%5Chbox%7B%20O%7D%7D_3%20%5Clongrightarrow%20%5Ctext%7B2K%7D%5Cstackrel%7B%5Chbox%7B%2B3%7D%7D%7B%5Chbox%7BN%7D%7D%5Ctext%7BO%7D_2%20%2B%20%5Cstackrel%7B%5Chbox%7B0%7D%7D%7B%5Chbox%7BO%7D%7D_2%5C%5C)
It is also a <em>reduction-oxidation reaction</em> because the <em>oxidation number of N decreases</em> from +5 to +3 and the <em>oxidation number of O increases</em> from -2 to 0.
The answer should be compound
D. is the answer
hope i could help
I'm not 100% sure that this is right but I think D. is correct.